Electrode and electrochemical device

ABSTRACT

An electrochemical device which is an alkali metal battery or an alkaline earth metal battery, wherein only a positive electrode is an electrode having a perfluoropolyether group-containing compound in a surface thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Rule 53(b) Continuation of U.S. application Ser.No. 16/346,639 filed May 1, 2019, which is a National Stage ofInternational Application No. PCT/JP2017/039819 filed Nov. 2, 2017,claiming priority based on Japanese Patent Application No. 2016-215523,filed Nov. 2, 2016, the disclosures of which are incorporated herein byreference in their respective entireties.

TECHNICAL FIELD

The present invention relates to an electrode and an electrochemicaldevice, and particularly, to an alkali metal ion battery such as alithium ion secondary battery.

BACKGROUND ART

Electrochemical devices, such as an alkali metal ion battery and anelectrochemical capacitor, can have characteristic features, such assmall size, high capacity and lightweight, and are used in variouselectronic devices. Particularly, a lithium ion secondary battery islight in weight and high in capacity and energy density. Because ofthis, the lithium ion secondary battery is used in a wide variety ofsmall electronic devices, particularly, portable devices such as a smartphone, a mobile phone, a tablet terminal, a video camera and a laptopcomputer.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Laid-Open No. 2010-44958

SUMMARY OF THE INVENTION Technical Problem

These electrochemical devices typically have a pair of electrodes and anelectrolyte. In the electrochemical devices, deterioration of theelectrodes and decomposition of the electrolyte may occur during use orstorage, with the result that capacity drops. Likewise, functionaldeterioration possibly occurs. For example, a lithium ion secondarybattery conceivably has a problem that the electrodes are deterioratedby charge-discharge cycles and thereby battery capacity reduces. Amethod for improving cycle characteristics is disclosed in PatentLiterature 1, in which a carboxylate or sulfonate of aperfluoropolyether group is added to an electrode to improve cyclecharacteristics. However, cycle characteristics improved by the methodis not sufficient.

In the circumstances, an object of the present invention is to providean electrochemical device, the function of which is suppressed fromdeteriorating during use or storage.

Solution to Problem

The present inventors conducted intensive studies with a view to solvingthe aforementioned problems. As a result, they have found thatfunctional deterioration during use or storage can be suppressed byadding a perfluoropolyether group in an electrode of an electrochemicaldevice. Based on the finding, they have arrived at the presentinvention.

According to a first aspect of the present invention, there is providedan electrode having a perfluoropolyether group-containing compound inthe surface.

According to a second aspect of the present invention, there is providedan electrochemical device comprising the electrode mentioned above.

Advantageous Effects of Invention

According to the present invention, it is possible to improve the cyclecapacity retention rate of an electrochemical device and suppress aresistance increase rate by using an electrode having aperfluoropolyether group-containing compound.

DESCRIPTION OF EMBODIMENTS

<Electrode>

The electrode of the present invention has a perfluoropolyethergroup-containing compound in a surface thereof. More specifically, theelectrode of the present invention (hereinafter, the electrode will beused for collectively referring to a positive electrode and a negativeelectrode) is constituted of an electrode material (hereinafter, theelectrode material will be used for collectively referring to a positiveelectrode material and a negative electrode material) and aperfluoropolyether group-containing compound present in the surface ofthe electrode material.

Perfluoropolyether Group-Containing Compound

As described above, the electrode of the present invention has aperfluoropolyether group-containing compound in a surface thereof.

The phrase “having a perfluoropolyether group-containing compound in asurface of the electrode” means that a perfluoropolyethergroup-containing compound is present in a surface of the electrode and,for example, includes a case where a perfluoropolyether group-containingcompound is present on a surface of an electrode material and a casewhere a perfluoropolyether group-containing compound and a raw-materialfor an electrode material are mixed and present in a surface layer ofthe electrode material.

In an embodiment, the electrode of the present invention has aperfluoropolyether group-containing compound in a surface thereof, i.e.,on the electrode material.

In a preferable embodiment, a perfluoropolyether group-containingcompound is present as a layer formed on a surface of an electrode.

The layer of a perfluoropolyether group-containing compound can be acoating layer preferably obtained by applying a reactiveperfluoropolyether group-containing compound to a surface of anelectrode material.

It is not necessary to form the coating layer over the whole surface ofthe electrode material and sufficient to form the coating layer on thesurface at which the electrode is in contact with an electrolyte.Preferably, the coating layer is formed over the whole surface of theelectrode material.

The reactive perfluoropolyether group-containing compound is not limitedas long as it can form a coating layer thereof on the electrode surface.

In a preferable embodiment, the reactive perfluoropolyethergroup-containing compound may be a compound represented by the followingformula (A1), (A2), (B1), (B2), (C1), (C2), (D1), (D2), (E1) or (E2).

In the formulae, Rf each independently represents an alkyl group having1 to 16 carbon atoms optionally substituted with one or more fluorineatoms.

In the phrase “the alkyl group having 1 to 16 carbon atoms optionallysubstituted with one or more fluorine atoms”, the phrase “the alkylgroup having 1 to 16 carbon atoms” may be linear or branched, and ispreferably a linear or branched alkyl group having 1 to 6 carbon atoms,particularly 1 to 3 carbon atoms, and more preferably a linear alkylgroup having 1 to 3 carbon atoms.

Rf preferably represents an alkyl group having 1 to 16 carbon atomssubstituted with one or more fluorine atoms, more preferably aCF₂H—C₁₋₁₅ fluoroalkylene group or a perfluoroalkyl group having 1 to 16carbon atoms, and further preferably a perfluoroalkyl group having 1 to16 carbon atoms.

The perfluoroalkyl group having 1 to 16 carbon atoms may be linear orbranched, and is preferably a linear or branched perfluoroalkyl grouphaving 1 to 6 carbon atoms, particularly 1 to 3 carbon atoms, and morepreferably a linear perfluoroalkyl group having 1 to 3 carbon atoms;specifically, —CF₃, —CF₂CF₃ or —CF₂CF₂CF₃.

In the above formulae, PFPE each independently represents—(OC₆F₁₂)_(a)—(OC₅F₁₀)_(b)—(OC₄F₈)_(c)—(OC₃F₆)_(d)—(OC₂F₄)_(e)—(OCF₂)_(f)—.

In the formulae, a, b, c, d, e and f each independently represent aninteger of 0 or more and 200 or less and the sum of a, b, c, d, e and fis at least 1. Preferably, a, b, c, d, e and f each independentlyrepresent an integer of 0 or more and 100 or less. Preferably, the sumof a, b, c, d, e and f is 5 or more, more preferably 10 or more, forexample, 10 or more and 100 or less. The repeating units enclosed inparentheses attached with a, b, c, d, e or f may be present in any orderin the formula.

These repeating units may be linear or branched and are preferablylinear. For example, the repeating unit, —(OC₆F₁₂)— may be, e.g.,—(OCF₂CF₂CF₂CF₂CF₂CF₂)—, —(OCF(CF₃)CF₂CF₂CF₂CF₂)—,—(OCF₂CF(CF₃)CF₂CF₂CF₂)—, —(OCF₂CF₂CF(CF₃)CF₂CF₂)—,—(OCF₂CF₂CF₂CF(CF₃)CF₂)—, —(OCF₂CF₂CF₂CF₂CF(CF₃))—; and is preferably—(OCF₂CF₂CF₂CF₂CF₂CF₂)—. The repeating unit, —(OC₅F₁₀)— may be, e.g.,—(OCF₂CF₂CF₂CF₂CF₂)—, —(OCF(CF₃)CF₂CF₂CF₂)—, —(OCF₂CF(CF₃)CF₂CF₂)—,—(OCF₂CF₂CF(CF₃)CF₂)—, —(OCF₂CF₂CF₂CF(CF₃))—; and is preferably—(OCF₂CF₂CF₂CF₂CF₂)—. The repeating unit, —(OC₄F₈)— may be any one of—(OCF₂CF₂CF₂CF₂)—, —(OCF(CF₃)CF₂CF₂)—, —(OCF₂CF(CF₃)CF₂)—,—(OCF₂CF₂CF(CF₃))—, —(OC(CF₃)₂CF₂)—, —(OCF₂C(CF₃)₂)—,—(OCF(CF₃)CF(CF₃))—, —(OCF(C₂F₅)CF₂)— and —(OCF₂CF(C₂F₅))—; andpreferably —(OCF₂CF₂CF₂CF₂)—. The repeating unit, —(OC₃F₆)—, may be anyone of —(OCF₂CF₂CF₂)—, —(OCF(CF₃)CF₂)— and —(OCF₂CF(CF₃))—, and ispreferably —(OCF₂CF₂CF₂)—. The repeating unit, —(OC₂F₄)— may be eitherone of —(OCF₂CF₂)— and —(OCF(CF₃))—, and is preferably —(OCF₂CF₂)—.

In an embodiment, PFPE each independently represents —(OC₃F₆)_(d)—wherein d represents an integer of 1 or more and 200 or less, preferably5 or more and 200 or less, and more preferably 10 or more and 200 orless. Preferably, PFPE each independently represents —(OCF₂CF₂CF₂)_(d)—wherein d represents an integer of 1 or more and 200 or less, preferably5 or more and 200 or less, and more preferably 10 or more and 200 orless or —(OCF(CF₃)CF₂)_(d)— wherein d represents an integer of 1 or moreand 200 or less, preferably 5 or more and 200 or less, and morepreferably 10 or more and 200 or less. More Preferably, PFPE eachindependently represents —(OCF₂CF₂CF₂)_(d)— wherein d represents aninteger of 1 or more and 200 or less, preferably 5 or more and 200 orless, and more preferably 10 or more and 200 or less.

In another embodiment, PFPE each independently represents—(OC₄F₈)_(c)—(OC₃F₆)_(d)—(OC₂F₄)_(e)—(OCF₂)_(f)— wherein c and d eachindependently represent an integer of 0 or more and 30 or less; e and feach independently represent an integer of 1 or more and 200 or less,preferably 5 or more and 200 or less, and more preferably 10 or more and200 or less; and the repeating units enclosed in parentheses attachedwith c, d, e and f may be present in any order in the formula.Preferably, PFPE each independently represents—(OCF₂CF₂CF₂CF₂)_(e)—(OCF₂CF₂CF₂)_(d)—(OCF₂CF₂)_(e)—(OCF₂)_(f)—. In anembodiment, PFPE each independently represents —(OC₂F₄)_(e)—(OCF₂)_(f)—wherein e and f each independently represent an integer of 1 or more and200 or less, preferably 5 or more and 200 or less, and more preferably10 or more and 200 or less; and the repeating units enclosed inparentheses attached with e and f may be present in any order in theformula.

In another embodiment, PFPE each independently represents a grouprepresented by —(R⁶-R⁷)_(q)—. In the formula, R⁶ represents OCF₂ orOC₂F₄ and preferably OC₂F₄. In the formula, R⁷ represents a groupselected from OC₂F₄, OC₃F₆, OC₄F₈, OC₅F₁₀ and OC₆F₁₂ or a combination of2 or 3 groups independently selected from these groups. Preferably, R⁷represents a group selected from OC₂F₄, OC₃F₆ and OC₄F₈ or a combinationof 2 or 3 groups independently selected from these groups. Examples ofthe combination of 2 or 3 groups independently selected from OC₂F₄,OC₃F₆ and OC₄F₈, include, but are not limited to, —OC₂F₄OC₃F₆—,—OC₂F₄OC₄F₈—, —OC₃F₆OC₂F₄—, —OC₃F₆OC₃F₆—, —OC₃F₆OC₄F₈—, —OC₄F₈OC₄F₈—,—OC₄F₈OC₃F₆—, —OC₄F₈OC₂F₄—, —OC₂F₄OC₂F₄OC₃F₆—, —OC₂F₄OC₂F₄OC₄F₈—,—OC₂F₄OC₃F₆OC₂F₄—, —OC₂F₄OC₃F₆OC₃F₆—, —OC₂F₄OC₄F₈OC₂F₄—,—OC₃F₆OC₂F₄OC₂F₄—, —OC₃F₆OC₂F₄OC₃F₆—, —OC₃F₆OC₃F₆OC₂F₄—, and—OC₄F₈OC₂F₄OC₂F₄—. The reference symbol q shown above represents aninteger of 2 to 100, and preferably an integer of 2 to 50. In the aboveformulae, OC₂F₄, OC₃F₆, OC₄F₈, OC₅F₁₀ and OC₆F₁₂ may be linear orbranched and preferably linear. In this embodiment, preferably, PFPEeach independently represents —(OC₂F₄—OC₃F₆)_(q)— or—(OC₂F₄—OC₄F₈)_(q)—.

In the above formulae, R¹ each independently in each occurrencerepresents a hydrogen atom or an alkyl group having 1 to 22 carbonatoms, and preferably an alkyl group having 1 to 4 carbon atoms.

In the above formulae, R² each independently in each occurrencerepresents a hydroxyl group or a hydrolyzable group.

The “hydrolyzable group” as used herein refers to a group that can beremoved from a main skeleton of a compound by a hydrolysis reaction.Examples of the hydrolyzable group include —OR, —OCOR, —O—N═CR₂, —NR₂,—NHR and halogen (in these formulae, R represents a substituted orunsubstituted alkyl group having 1 to 4 carbon atoms), and preferably is—OR (i.e., alkoxy group). Examples of R include an unsubstituted alkylgroup such as a methyl group, an ethyl group, a propyl group, anisopropyl group, a n-butyl group and an isobutyl group; and asubstituted alkyl group such as a chloromethyl group. Of them, an alkylgroup, particularly, an unsubstituted alkyl group is preferable; and amethyl group or an ethyl group is more preferable. The hydroxyl group,although it is not limited, may be a group generated by hydrolyzation ofa hydrolyzable group.

In the above formulae, R¹¹ each independently in each occurrencerepresents a hydrogen atom or a halogen atom. The halogen atom ispreferably an iodine atom, a chlorine atom or a fluorine atom, and morepreferably a fluorine atom.

In the above formulae, R¹² each independently in each occurrencerepresents a hydrogen atom or a lower alkyl group. The lower alkyl groupis preferably an alkyl group having 1 to 20 carbon atoms, and morepreferably an alkyl group having 1 to 6 carbon atoms, such as a methylgroup, an ethyl group and a propyl group.

In the above formulae, n independently represents an integer of 0 to 3in each (SiR¹ _(n)R² _(3-n)) unit, preferably an integer of 0 to 2, andmore preferably 0. It is noted that, n does not simultaneously represent0 in the all formulae. In other words, in the formulae, at least one R²is present.

In the above formulae, preferably t each independently represents aninteger of 1 to 10. In a preferable embodiment, t represents an integerof 1 to 6. In another preferable embodiment, t represents an integer of2 to 10, and preferably 2 to 6.

In the above formulae, X² each independently in each occurrencerepresents a single bond or a divalent organic group. X² representspreferably an alkylene group having 1 to 20 carbon atoms, and morepreferably —(CH₂)_(u)— wherein u represents an integer of 0 to 2.

In the above formulae, R^(a) each independently in each occurrencerepresents —Z—SiR⁷¹ _(p)R⁷² _(q)R⁷³ _(r).

In the formula, Z each independently in each occurrence represents anoxygen atom or a divalent organic group.

Z herein preferably represents a divalent organic group. In a preferableembodiment, Z is not a group which forms a siloxane bond with a Si atom(to which R^(a) is bound) present at an end of the molecular backbone informula (C1) or formula (C2).

Z herein represents preferably a C₁₋₆ alkylene group,—(CH₂)_(g)—O—(CH₂)_(h)— wherein g represents an integer of 1 to 6; and hrepresents an integer of 1 to 6 or -phenylene-(CH₂)_(i)— wherein irepresents an integer of 0 to 6; and more preferably a C₁₋₃ alkylenegroup. These groups may be substituted with at least one substituentselected from, e.g., a fluorine atom, a C₁₋₆ alkyl group, a C₂₋₆ alkenylgroup and a C₂₋₆ alkynyl group.

In the above formulae, R⁷¹ each independently in each occurrencerepresents R^(a′). R^(a′) is the same as defined in R^(a).

In R^(a), the number of Si atoms linearly connected via group Z is atmost 5. In R^(a), if at least single R⁷¹ is present, the number of Siatoms linearly connected via group Z is two or more; and the number ofSi atoms linearly connected via group Z is at most 5. Note that, “thenumber of Si atoms linearly connected via group Z in R^(a)” is equal tothe number of repeats of —Z—Si— linearly connected with each other inR^(a).

More specifically, an example of the case where Si atoms are connectedvia group Z in R^(a) is shown below:

In the above formula, mark * represents a site to be bound to the Siatom of the main chain; mark “ . . . ” means that a predetermined groupexcept ZSi is bound. More specifically, if three bonds of a Si atom areall expressed by “ . . . ”, the repeat of ZSi ends there. The numeral onthe right shoulder of Si indicates the number (occurrence number) of Siatoms linearly connected via group Z and counted from the side *. Todescribe more specifically, a chain having ZSi repeats and ended by Si²means that “the number of Si atoms linearly connected via group Z inR^(a)” is 2. Similarly, chains having ZSi repeats and ended by Si³, Si⁴and Si⁵ means that “the number of Si atoms linearly connected via groupZ in R^(a)” are 3, 4 and 5, respectively. It is noted that, as isapparent from the above formulae, a plurality of ZSi chains are presentin R^(a); and it is not necessary that these ZSi chains all have thesame length and the lengths of the chains may be arbitrarily set.

In a preferable embodiment, as shown below, “the numbers of Si atomslinearly connected via group Z in R^(a)” in all chains is one (the leftformula below) or two (the right formula below).

In an embodiment, the number of Si atoms linearly connected via group Zin R^(a) is one or two and preferably one.

In the formula, R⁷² each independently in each occurrence represents ahydroxyl group or a hydrolyzable group.

Preferably, R⁷² represents —OR wherein R represents a substituted orunsubstituted C₁₋₃ alkyl group, and more preferably a methyl group.

In the formula, R⁷³ each independently in each occurrence represents ahydrogen atom or a lower alkyl group. The lower alkyl group ispreferably an alkyl group having 1 to 20 carbon atoms, more preferablyan alkyl group having 1 to 6 carbon atoms, and further preferably amethyl group.

In the formula, p each independently in each occurrence represents aninteger of 0 to 3; q each independently in each occurrence represents aninteger of 0 to 3; r each independently in each occurrence represents 0to 3; and, the sum of p, q and r is 3.

In a preferable embodiment, in R^(a)′ at an end of R^(a) (if R^(a)′ isnot present, R^(a) itself), q represents preferably an integer of 2 ormore; for example, an integer of 2 or 3, and more preferably 3.

In a preferable embodiment, R^(a) may have at least one —Si(—Z—SiR⁷²_(q)R⁷³ _(r))₂ or —Si(—Z—SiR⁷² _(q)R⁷³ _(r))₃ at an end, and preferably—Si(—Z—SiR⁷² _(q)R⁷³ _(r))₃. In the formula, the unit of (—Z—SiR⁷²_(q)R⁷³ _(r)) is preferably (—Z—SiR⁷² ₃). In a further preferableembodiment, the ends of R^(a) may be all —Si(—Z—SiR⁷² _(q)R⁷³ _(r))₃ andpreferably —Si(—Z—SiR⁷² ₃)₃.

In the above formulae (C1) and (C2), at least one R⁷² is present.

In the above formulae, R^(b) each independently in each occurrencerepresents a hydroxyl group or a hydrolyzable group.

R^(b) preferably represents a hydroxyl group, —OR, —OCOR, —O—N═C(R)₂,—N(R)₂, —NHR or halogen (in these formulae, R represents a substitutedor unsubstituted alkyl group having 1 to 4 carbon atoms) and preferably—OR. Examples of R include an unsubstituted alkyl group such as a methylgroup, an ethyl group, a propyl group, an isopropyl group, a n-butylgroup and an isobutyl group; and a substituted alkyl group such as achloromethyl group. Of them, an alkyl group, particularly anunsubstituted alkyl group, is preferable, a methyl group or an ethylgroup is more preferable. The hydroxyl group, although it is notlimited, may be generated by hydrolysis of a hydrolyzable group. Morepreferably, R^(c) is —OR wherein R represents a substituted orunsubstituted C₁-3 alkyl group, and more preferably a methyl group.

In the above formulae, R^(c) each independently in each occurrencerepresents a hydrogen atom or a lower alkyl group. The lower alkyl grouprepresents preferably an alkyl group having 1 to 20 carbon atoms, morepreferably an alkyl group having 1 to 6 carbon atoms and furtherpreferably a methyl group.

In the above formulae, k each independently in each occurrencerepresents an integer of 0 to 3; 1 each independently in each occurrencerepresents an integer 0 to 3; m each independently in each occurrencerepresents an integer of 0 to 3. Note that, the sum of k, 1 and m is 3.

In the above formulae, R^(d) each independently in each occurrencerepresents —Z′—CR⁸¹ _(p′)R⁸² _(q′)R⁸³ _(r).

Z′ each independently in each occurrence represents an oxygen atom or adivalent organic group.

Z′ is preferably a C₁₋₆ alkylene group, —(CH₂)_(g)—O—(CH₂)_(h)— whereing represents an integer of 0 to 6; for example, an integer of 1 to 6,and h represents an integer of 0 to 6; for example, an integer of 1 to 6or, -phenylene-(CH₂)_(i)— wherein i represents an integer of 0 to 6, andmore preferably a C₁₋₃ alkylene group. These groups may be substitutedwith at least one substituent selected from, for example, a fluorineatom, a C₁₋₆ alkyl group, a C₂₋₆ alkenyl group and a C₂₋₆ alkynyl group.

In the formula, R⁸¹ each independently in each occurrence representsR^(d′). R^(d′) is the same as defined in R^(d).

In R^(d), the number of C atoms linearly connected via group Z′ is atmost 5. In R^(d), if at least one R⁸¹ is present, the number of Si atomslinearly connected via group Z′ is two or more; and the number of Catoms linearly connected via group Z′ is at most 5. Note that, “thenumber of C atoms linearly connected via group Z′ in R^(d)” is equal tothe number of repeats of —Z′—C— linearly connected in R^(d).

In a preferable embodiment, as shown below, “the numbers of C atomslinearly connected via group Z′ in R^(d)” in all chains is one (the leftformula below) or two (the right formula below).

In an embodiment, the number of C atoms linearly connected via group Z′in R^(d) is one or two and preferably one.

In the formula, R⁸² represents —Y—SiR⁸⁵ _(j)R⁸⁶ _(3-j).

Y each independently in each occurrence represents a divalent organicgroup.

In a preferable embodiment, Y represents a C₁₋₆ alkylene group,—(CH₂)_(g′)—O—(CH₂)_(h′)— wherein g′ represents an integer of 0 to 6;for example, an integer of 1 to 6, and h′ represents an integer of 0 to6; for example, an integer of 1 to 6 or -phenylene-(CH₂)_(i′)— whereini′ represents an integer of 0 to 6. These groups may be substituted, forexample, with at least one substituent selected from a fluorine atom, aC₁₋₆ alkyl group, a C₂₋₆ alkenyl group and a C₂₋₆ alkynyl group.

In an embodiment, Y may be a C₁₋₆ alkylene group or-phenylene-(CH₂)_(i′)—. If Y is either one of these, light resistance,particularly ultraviolet resistance can be improved.

R⁸⁵ each independently in each occurrence represents a hydroxyl group ora hydrolyzable group. Examples of the “hydrolyzable group” are the sameas those mentioned above.

Preferably, R⁸⁵ represents —OR wherein R represents a substituted orunsubstituted a C₁₋₃ alkyl group, more preferably an ethyl group or amethyl group, and particularly, a methyl group.

R⁸⁶ each independently in each occurrence represents a hydrogen atom ora lower alkyl group. The lower alkyl group is preferably an alkyl grouphaving 1 to 20 carbon atoms, more preferably an alkyl group having 1 to6 carbon atoms, and further preferably a methyl group.

Reference symbol, j independently represents an integer of 1 to 3 ineach (—Y—SiR⁸⁵ _(j)R⁸⁶ _(3-j) unit), preferably an integer of 2 or 3,and more preferably, 3.

R⁸³ each independently in each occurrence represents a hydrogen atom ora lower alkyl group. The lower alkyl group is preferably an alkyl grouphaving 1 to 20 carbon atoms, more preferably an alkyl group having 1 to6 carbon atoms, and further preferably a methyl group.

In the formula, p′ each independently in each occurrence represents aninteger 0 to 3; q′ each independently in each occurrence represents aninteger of 0 to 3; r′ each independently in each occurrence representsan integer of 0 to 3; and the sum of p′, q′ and r′ is 3.

In a preferable embodiment, in R^(d)′ at an end of R^(d) (if R^(d)′ isnot present, R^(a) itself), q′ represents preferably 2 or more; forexample, 2 or 3, and more preferably 3.

In the above formulae, Re each independently in each occurrencerepresents —Y—SiR⁸⁵ _(j)R⁸⁶ _(3-j), wherein Y, R⁸⁵, R⁸⁶ and j are thesame as defined in R⁸² in the above.

In the above formulae, R^(f) each independently in each occurrencerepresents a hydrogen atom or a lower alkyl group. The lower alkyl groupis preferably an alkyl group having 1 to 20 carbon atoms, morepreferably an alkyl group having 1 to 6 carbon atoms, and furtherpreferably a methyl group.

In the formulae, k′ each independently in each occurrence represents aninteger of 0 to 3; 1′ each independently in each occurrence representsan integer of 0 to 3; and m′ each independently in each occurrencerepresents an integer of 0 to 3; and the sum of k′, 1′ and m′ is 3.

In an embodiment, at least one k′ is 2 or 3 and preferably 3.

In an embodiment, k′ is 2 or 3 and preferably 3.

In an embodiment, 1′ is 2 or 3 and preferably 3.

In the above formulae (D1) and (D2), at least one q′ is 2 or 3 or atleast one 1′ is 2 or 3. In other words, in the formulae, at least twoY—SiR⁸⁵ _(j)R⁸⁶ _(3-j) groups are present.

In the above formulae, A each independently in each occurrencerepresents —OH, —SH, —NH₂, —COOH or —SO₃H. Preferably, A may be —OH.

In the above formulae, X¹ each independently represents a single bond ora 2 to 10 valent organic group. X¹ in compounds represented by formulae(A1) and (A2) is interpreted as a linker connecting a perfluoropolyethermoiety (i.e., Rf-PFPE moiety or —PFPE- moiety) which mainly provides,e.g., water-repellency and surface lubricity, and a silane moiety (i.e.,a group enclosed in parentheses attached with a) which provides bindingability to a substrate. Thus, X¹ may be any organic group as long as thecompounds represented by formulae (A1) and (A2) can be stably present.

In the above formulae, a represents an integer of 1 to 9, and a′represents an integer of 1 to 9. The integers represented by α and α′can vary depending on the valence of X¹. In formula (A1), the sum of αand α′ is equal to the valence of X¹. For example, if X¹ is a 10 valentorganic group, the sum of α and α′ is 10; for example, a case where α is9 and α′ is 1, and α is 5 and α′ is 5, or α is 1 and α′ is 9, can beconsidered. If X¹ is a divalent organic group, α and α′ each are 1. Informula (A2), the value of α is obtained by subtracting 1 from thevalence of X¹.

X¹ preferably represents a 2 to 7 valent organic group, more preferablya 2 to 4 valent organic group, and further preferably a divalent organicgroup.

In an embodiment, X¹ represents 2 to 4 valent organic group; αrepresents an integer of 1 to 3; and α′ represents 1.

In another embodiment, X¹ represents a divalent organic group; αrepresents 1; and α′ represents 1. In this case, formulae (A1) and (A2)are represented by the following formulae (A1′) and (A2′), respectively.

In the above formulae, X⁵ each independently represents a single bond ora 2 to 10 valent organic group. X⁵ in compounds represented by formulae(B1) and (B2) is interpreted as a linker connecting a perfluoropolyethermoiety (Rf-PFPE moiety or -PFPE- moiety) which mainly provides, e.g.,water-repellency and surface lubricity, and a silane moiety (i.e., —SiR¹_(n)R² _(3-n)) which provides binding ability to a substrate. Thus, X⁵may be any organic group as long as compounds represented by formulae(B1) and (B2) can be stably present.

In the above formulae, β represents an integer of 1 to 9 and β′represents an integer of 1 to 9. The integers represented by β and β′are determined in accordance with the valence of X⁵. In formula (B1),the sum of β and β′ is equal to the valence of X⁵. For example, if X⁵represents a 10-valent organic group, the sum of β and β′ is 10; forexample, a case where β is 9 and β′ is 1, β is 5 and β′ is 5, or β is 1and β′ is 9, can be considered. If X⁵ is a divalent organic group, β andβ′ each are 1. In formula (B2), the value of β is obtained bysubtracting 1 from the valence of X⁵.

X⁵ preferably represents a 2 to 7 valent organic group, more preferablya 2 to 4 valent organic group, and further preferably a divalent organicgroup.

In an embodiment, X⁵ represents a 2 to 4 valent organic group; βrepresents an integer of 1 to 3; and β′ represents 1.

In another embodiment, X⁵ represents a divalent organic group; βrepresents 1; and β′ represents 1. In this case, formulae (B1) and (B2)are represented by the following formulae (B1′) and (B2′), respectively.[Formula 6]Rf-PFPE-X⁵—SiR¹ _(n)R² _(3-n)  (B1′)R² _(3-n)R¹ _(n)Si-X⁵-PFPE-X⁵—SiR¹ _(n)R² _(3-n)  (B2′)

In the above formulae, X⁷ each independently represents a single bond ora 2 to 10 valent organic group. X⁷ in compounds represented by formulae(C1) and (C2) is interpreted as a linker connecting a perfluoropolyethermoiety (Rf-PFPE moiety or -PFPE- moiety) which mainly provides, e.g.,water-repellency and surface lubricity, and a silane moiety (i.e.,—SiR^(a) _(k)R^(b) _(l)R^(c) _(m) group) which provides binding abilityto a substrate. Thus, X⁷ may be any organic group as long as compoundsrepresented by formulae (C1) and (C2) can be stably present.

In the above formulae, γ represents an integer of 1 to 9 and γ′represents an integer of 1 to 9. The integers represented by γ and γ′are determined in accordance with the valence of X⁷. In formula (C1),the sum of γ and γ′ is equal to the valence of X⁷. For example, if X⁷represents a 10 valent organic group, the sum of γ and γ′ is 10; forexample, a case where γ is 9 and γ′ is 1; γ is 5 and γ′ is 5 or γ is 1and γ′ is 9, can be considered. If X⁷ is a divalent organic group, γ andγ′ each are 1. In formula (C2), the value of γ is obtained bysubtracting 1 from the valence of X⁷.

X⁷ represents preferably 2 to 7 valent organic group, more preferably 2to 4 valent organic group, and further preferably a divalent organicgroup.

In an embodiment, X⁷ represents a 2 to 4 valent organic group; γrepresents an integer of 1 to 3 and γ′ represents 1.

In another embodiment, X⁷ represents a divalent organic group; γrepresents 1 and γ′ represents 1. In this case, formulae (C1) and (C2)are represented by the following formulae (C1′) and (C2′), respectively.[Formula 7]Rf-PFPE-X⁷—SiR^(a) _(k)R^(b) _(l)R^(c) _(m)  (C1′)R^(c) _(m)R^(b) _(l)R^(a) _(k)Si-X⁷-PFPE-X⁷—SiR^(a) _(k)R^(b) _(l)R^(c)_(m)  (C2′)

In the above formulae, X⁹ each independently represents a single bond ora 2 to 10 valent organic group. X⁹ in compounds represented by formulae(D1) and (D2) is interpreted as a linker connecting a perfluoropolyethermoiety (i.e., Rf-PFPE moiety or -PFPE- moiety) which mainly provides,e.g., water-repellency and surface lubricity, and a moiety (i.e., agroup enclosed in parentheses attached with δ) providing binding abilityto a substrate. Thus, X⁹ may be any organic group as long as thecompounds represented by formulae (D1) and (D2) can be stably present.

In the above formulae, δ represents an integer of 1 to 9 and δ′represents an integer of 1 to 9. The integers represented by δ and δ′can vary depending on the valence of X⁹. In formula (D1), the sum of δand δ′ is equal to as the valence of X⁹. For example, if X⁹ is a 10valent organic group, the sum of δ and δ′ is 10; for example, a casewhere δ is 9 and δ′ is 1; δ is 5 and δ′ is 5, or δ is 1 and δ ′ is 9,can be considered. If X⁹ is a divalent organic group, δ and δ′ eachare 1. In formula (D2), the value of δ is obtained by subtracting 1 fromthe valence of X⁹

X⁹ preferably represents a 2 to 7 valent organic group, more preferablya 2 to 4 valent organic group, and further preferably a divalent organicgroup.

In an embodiment, X⁹ represents a 2 to 4 valent organic group; δrepresents an integer of 1 to 3; and δ′ represents 1.

In another embodiment, X⁹ represents a divalent organic group; δrepresents 1; and δ′ represents 1. In this case, formulae (D1) and (D2)are represented by the following formulae (D1′) and (D2′).[Formula 8]Rf-PFPE-X⁹—CR^(d) _(k′)R^(e) _(l′)R^(f) _(m′)  (D1′)R^(f) _(m′)R^(e) _(l′)R^(d) _(k′)C_(δ)—X⁹-PFPE-X⁹—CR^(d) _(k′)R^(e)_(l′)R^(f) _(m′)  (D2′)

In the above formulae, X³ each independently represents a single bond ora 2 to 10 valent organic group. X³ in compounds represented by formulae(E1) and (E2) is interpreted as a linker, connecting aperfluoropolyether moiety (i.e., Rf-PFPE moiety or -PFPE- moiety) whichmainly provides, e.g., water-repellency and surface lubricity, and amoiety (i.e., group A) providing binding ability to a substrate. Thus,X³ may be any organic group as long as the compounds represented byformulae (E1) and (E2) can be stably present.

In the above formulae, ε represents an integer of 1 to 9 and ε′represents an integer of 1 to 9. The integers represented by ε and ε′can vary depending on the valence of X³. In formula (E1), the sum of εand ε′ is equal to the valence of X³. For example, if X³ represents a 10valent organic group, the sum of ε and ε′ is 10; for example, a casewhere ε is 9 and ε′ is 1; ε is 5 and ε′ is 5, or ε is 1 and ε′ is 9 canbe considered. If X³ is a divalent organic group, ε and ε′ each are 1.In formula (E2), the value of ε is obtained by subtracting 1 from thevalence of X⁹.

X³ preferably represents a 2 to 7 valent organic group, more preferablya 2 to 4 valent organic group and further preferably a divalent organicgroup.

In an embodiment, X³ represents a 2 to 4 valent organic group; εrepresents an integer of 1 3; and ε′ represents 1.

In another embodiment, X³ represents a divalent organic group; εrepresents 1; and ε′ represents 1. In this case, formulae (E1) and (E2)are represented by the following formulae (E1′) and (E2′).[Formula 9]Rf-PFPE-X³-A  (E1′)A-X³-PFPE-X³-A  (E2′)

In a preferable embodiment, X¹, X³, X⁵, X⁷ and X⁹, although they are notlimited, may each independently represent, for example, a divalent grouprepresented by the following formula:—(R³¹)_(p1)—(X^(a))_(q1)—wherein

R³¹ represents a single bond, —(CH₂)_(s′)— or o-, m- or p-phenylenegroup and preferably —(CH₂)_(s′)—,

wherein s′ represents an integer of 1 to 20, preferably 1 to 6, morepreferably 1 to 3 and still further preferably 1 or 2,

X^(a) represents —(X^(b))_(l′)—,

wherein X^(b) each independently in each occurrence represents a groupselected from the group consisting of —O—, —S—, o-, a m- or p-phenylenegroup, —C(O)O—, —Si(R³³)₂—, —(Si(R³³)₂O)_(m″)—Si(R³³)₂—, —CONR³⁴—,—O—CONR³⁴—, —NR³⁴— and —(CH₂)_(n′)—,

wherein R³³ each independently in each occurrence represents a phenylgroup, a C₁₋₆ alkyl group or a C₁₋₆ alkoxy group, preferably a phenylgroup or a C₁₋₆ alkyl group, and more preferably a methyl group,

R³⁴ each independently in each occurrence represents a hydrogen atom, aphenyl group or a C₁₋₆ alkyl group (preferably a methyl group),

m″ each independently in each occurrence represents an integer of 1 to100 and preferably an integer of 1 to 20,

n′ each independently in each occurrence represents an integer of 1 to20, preferably an integer of 1 to 6, and more preferably an integer of 1to 3,

l′ represents an integer of 1 to 10, preferably an integer of 1 to 5,and more preferably an integer of 1 to 3, and

p1 represents 0 or 1, and

q1 represents 0 or 1;

herein, at least one of p1 and q1 represents 1 and the repeating unitsenclosed in parentheses attached with p1 or q1 may be present in anyorder; and R³¹ and X^(a) (typically, hydrogen atoms of R³¹ and X^(a))are optionally substituted with at least one substituent selected from afluorine atom, a C₁₋₃ alkyl group and a C₁₋₃ fluoroalkyl group.

Preferably, X¹, X³, X⁵, X⁷ and X⁹ each independently represent—(R³¹)_(p1)—(X^(a))_(q1)—R³²—. R³² represents a single bond,—(CH₂)_(t′)— or o-, m- or a p-phenylene group, and preferably—(CH₂)_(t′)—, wherein t′ represents an integer of 1 to 20, preferably aninteger of 2 to 6, and more preferably an integer of 2 or 3. R³²(typically, a hydrogen atom of R³²) herein is optionally substitutedwith at least one substituent selected from a fluorine atom, a C₁₋₃alkyl group and a C₁₋₃ fluoroalkyl group.

Preferably, X¹, X³, X⁵, X⁷ and X⁹ may each independently represent aC₁₋₂₀ alkylene group,

—R³¹—X^(c)—R³²— or

—X^(d)—R³²—

wherein R³¹ and R³² are the same as defined above.

More preferably, X¹, X³, X⁵, X⁷ and X⁹ each independently represent

a C₁₋₂₀ alkylene group,

—(CH₂)_(s′)—X^(c)—,

—(CH₂)_(s′)—X^(c)—(CH₂)_(t′)—

—X^(d)— or

—X^(d)—(CH₂)_(t′)—

wherein s′ and t′ are the same as defined above.

In the above formulae, X^(c) represents

—O—,

—S—,

—C(O)O—,

—CONR³⁴—,

—O—CONR³⁴—,

—Si(R³³)₂—,

—(Si(R³³)₂O)_(m″)—Si(R³³)₂—,

—O—(CH₂)_(u′)—(Si(R³³)₂O)_(m″)—Si(R³³)₂—,

—O—(CH₂)_(u′)—Si(R³³)₂—O—Si(R³³)₂—CH₂CH₂—Si(R³³)₂—O—Si(R³³)₂—,

—O—(CH₂)_(u′)—Si(OCH₃)₂OSi(OCH₃)₂—,

—CONR³⁴—(CH₂)_(u′)—(Si(R³³)₂O)_(m″)—Si(R³³)₂—,

—CONR³⁴—(CH₂)_(u′)—N(R³⁴)—, or

—CONR³⁴-(o-, m- or p-phenylene)-Si(R³³)₂—,

wherein R³³, R³⁴ and m″ are the same as defined above,

u′ represents an integer of 1 to 20, preferably an integer of 2 to 6,more preferably an integer of 2 or 3; and X^(c) preferably represents—O—.

In the above formulae, X^(d) represents

—S—,

—C(O)O—,

—CONR³⁴—,

—CONR³⁴—(CH₂)_(u′)—(Si(R³³)₂O)_(m″)—Si(R³³)₂—,

—CONR³⁴—(CH₂)_(u′)—N(R³⁴)—, or

—CONR³⁴-(o-, m- or p-phenylene)-Si(R³³)₂—,

wherein individual reference symbols are the same as defined above.

More preferably, X¹, X³, X⁵, X⁷ and X⁹ may each independently represent

a C₁₋₂₀ alkylene group,

—(CH₂)_(s′)—X^(c)—(CH₂)_(t′)— or

—X^(d)—(CH₂)_(t′)—,

wherein individual reference symbols are the same as defined above.

Still more preferably, X¹, X³, X⁵, X⁷ and X⁹ each independentlyrepresent a C₁₋₂₀ alkylene group,

—(CH₂)_(s′)—O—(CH₂)_(t′)—,

—(CH₂)_(s′)—(Si(R³³)₂O)_(m″)—Si(R³³)₂—(CH₂)_(t′)—,

—(CH₂)_(s′)—O—(CH₂)_(u′)—(Si(R³³)₂O)_(m″)—Si(R³³)₂—(CH₂)_(t′)—, or

—(CH₂)_(s′)—O—(CH₂)_(t′)—Si(R³³)₂—(CH₂)_(u′)—Si(R³³)₂—(C_(v)H_(2v))—

wherein R³³, m″, s′, t′ and u′ are the same as defined above; vrepresents an integer of 1 to 20, preferably an integer of 2 to 6 andmore preferably an integer of 2 or 3.

In the above formula, —(C_(v)H_(2v))— may be linear or branched and maybe, for example, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)— or —CH(CH₃)CH₂—.

Groups represented by X¹, X³, X⁵, X⁷ and X⁹ each independently areoptionally substituted with at least one substituent selected from afluorine atom, a C₁₋₃ alkyl group and a C₁₋₃ fluoroalkyl group(preferably a C₁₋₃ perfluoroalkyl group).

In an embodiment, groups represented by X¹, X³, X⁵, X⁷ and X⁹ may beeach independently groups except a —O—C₁₋₆ alkylene group.

In another embodiment, examples of the groups represented by X¹, X³, X⁵,X⁷ and X⁹, include those mentioned below:

wherein R⁴¹ each independently represents a hydrogen atom, a phenylgroup, an alkyl group having 1 to 6 carbon atoms or a C₁₋₆ alkoxy group,and preferably a methyl group; and

D represents a group selected from

—CH₂O(CH₂)₂—,

—CH₂O(CH₂)₃—,

—CF₂O(CH₂)₃—,

—(CH₂)₂—,

—(CH₂)₃—,

—(CH₂)₄—,

—CONH—(CH₂)₃—,

—CON(CH₃)—(CH₂)₃—,

—CON(Ph)-(CH₂)₃— (wherein Ph stands for phenyl) and

a group represented by the following formula:

wherein R⁴² each independently represents a hydrogen atom, a C₁₋₆ alkylgroup or a C₁₋₆ alkoxy group, preferably a methyl group or a methoxygroup, and more preferably a methyl group,

E represents —(CH₂)_(n)— (n represents an integer of 2 to 6), and

D binds to a molecular backbone, PFPE, and E binds to a group oppositeto PFPE.

Specific examples of X¹, X³, X⁵, X⁷ and X⁹ include, for example,

—CH₂O(CH₂)₂—,

—CH₂O(CH₂)₃—,

—CH₂O(CH₂)₆—,

—CH₂O(CH₂)₃Si(CH₃)₂OSi(CH₃)₂(CH₂)₂—,

—CH₂O(CH₂)₃Si(CH₃)₂OSi(CH₃)₂OSi(CH₃)₂(CH₂)₂—,

—CH₂O(CH₂)₃Si(CH₃)₂O(Si(CH₃)₂O)₂Si(CH₃)₂(CH₂)₂—,

—CH₂O(CH₂)₃Si(CH₃)₂O(Si(CH₃)₂O)₃Si(CH₃)₂(CH₂)₂—,

—CH₂O(CH₂)₃Si(CH₃)₂O(Si(CH₃)₂O)₁₀Si(CH₃)₂(CH₂)₂—,

—CH₂O(CH₂)₃Si(CH₃)₂O(Si(CH₃)₂O)₂₀Si(CH₃)₂(CH₂)₂—,

—CH₂OCF₂CHFOCF₂—,

—CH₂OCF₂CHFOCF₂CF₂—,

—CH₂OCF₂CHFOCF₂CF₂CF₂—,

—CH₂OCH₂CF₂CF₂OCF₂—,

—CH₂OCH₂CF₂CF₂OCF₂CF₂—,

—CH₂OCH₂CF₂CF₂OCF₂CF₂CF₂—,

—CH₂OCH₂CF₂CF₂OCF(CF₃)CF₂OCF₂—,

—CH₂OCH₂CF₂CF₂OCF(CF₃)CF₂OCF₂CF₂—,

—CH₂OCH₂CF₂CF₂OCF(CF₃)CF₂OCF₂CF₂CF₂—,

—CH₂OCH₂CHFCF₂OCF₂—,

—CH₂OCH₂CHFCF₂OCF₂CF₂—,

—CH₂OCH₂CHFCF₂OCF₂CF₂CF₂—,

—CH₂OCH₂CHFCF₂OCF(CF₃)CF₂OCF₂—,

—CH₂OCH₂CHFCF₂OCF(CF₃)CF₂OCF₂CF₂—,

—CH₂OCH₂CHFCF₂OCF(CF₃)CF₂OCF₂CF₂CF₂—

—CH₂OCH₂(CH₂)₇CH₂Si(OCH₃)₂OSi(OCH₃)₂(CH₂)₂Si(OCH₃)₂OSi(OCH₃)₂(CH₂)₂—,

—CH₂OCH₂CH₂CH₂Si(OCH₃)₂OSi(OCH₃)₂(CH₂)₃—,

—CH₂OCH₂CH₂CH₂Si(OCH₂CH₃)₂OSi(OCH₂CH₃)₂(CH₂)₃—,

—CH₂OCH₂CH₂CH₂Si(OCH₃)₂OSi(OCH₃)₂(CH₂)₂—,

—CH₂OCH₂CH₂CH₂Si(OCH₂CH₃)₂OSi(OCH₂CH₃)₂(CH₂)₂—,

—(CH₂)₂—,

—(CH₂)₃—,

—(CH₂)₄—,

—(CH₂)₅—,

—(CH₂)₆—,

—CONH—(CH₂)₃—,

—CON(CH₃)—(CH₂)₃—,

—CON(Ph)-(CH₂)₃— (wherein Ph stands for phenyl),

—CONH—(CH₂)₆—,

—CON(CH₃)—(CH₂)₆—,

—CON(Ph)-(CH₂)₆— (wherein Ph stands for phenyl),

—CONH—(CH₂)₂NH(CH₂)₃—,

—CONH—(CH₂)₆NH(CH₂)₃—,

—CH₂O—CONH—(CH₂)₃—,

—CH₂O—CONH—(CH₂)₆—,

—S—(CH₂)₃—,

—(CH₂)₂S(CH₂)₃—,

—CONH—(CH₂)₃Si(CH₃)₂OSi(CH₃)₂(CH₂)₂—,

—CONH—(CH₂)₃Si(CH₃)₂OSi(CH₃)₂OSi(CH₃)₂(CH₂)₂—,

—CONH—(CH₂)₃Si(CH₃)₂O(Si(CH₃)₂O)₂Si(CH₃)₂(CH₂)₂—,

—CONH—(CH₂)₃Si(CH₃)₂O(Si(CH₃)₂O)₃Si(CH₃)₂(CH₂)₂—,

—CONH—(CH₂)₃Si(CH₃)₂O(Si(CH₃)₂O)₁₀Si(CH₃)₂(CH₂)₂—,

—CONH—(CH₂)₃Si(CH₃)₂O(Si(CH₃)₂O)₂₀Si(CH₃)₂(CH₂)₂—

—C(O)O—(CH₂)₃—,

—C(O)O—(CH₂)₆—,

—CH₂—O—(CH₂)₃—Si(CH₃)₂—(CH₂)₂—Si(CH₃)₂—(CH₂)₂—,

—CH₂—O—(CH₂)₃—Si(CH₃)₂—(CH₂)₂—Si(CH₃)₂—CH(CH₃)—,

—CH₂—O—(CH₂)₃—Si(CH₃)₂—(CH₂)₂—Si(CH₃)₂—(CH₂)₃—,

—CH₂—O—(CH₂)₃—Si(CH₃)₂—(CH₂)₂—Si(CH₃)₂—CH(CH₃)—CH₂—,

—OCH₂—,

—O(CH₂)₃—,

—OCFHCF₂—,

and a group represented by the following formula:

In another embodiment, X¹, X³, X⁵, X⁷ and X⁹ each independentlyrepresent a group represented by the formula:—(R¹⁶)_(x)—(CFR¹⁷)_(y)—(CH₂)_(z)—, wherein, x, y and z eachindependently represent an integer of 0 to 10 and the sum of x, y and zis 1 or more, the repeating units enclosed in parentheses may be presentin any order.

In the above formula, R¹⁶ each independently in each occurrencerepresents an oxygen atom, phenylene, carbazolylene, —NR²⁶— (wherein R²⁶represents a hydrogen atom or an organic group) or a divalent organicgroup. Preferably, R¹⁶ represents an oxygen atom or a divalent polargroup.

Examples of the “divalent polar group” include, but are not limited to,—C(O)—, —C(═NR²⁷)— and —C(O)NR²⁷— (wherein R²⁷ represents a hydrogenatom or a lower alkyl group). The “lower alkyl group” is, for example,an alkyl group having 1 to 6 carbon atoms, such as methyl, ethyl andn-propyl which are optionally substituted with one or more fluorineatoms.

In the above formulae, R¹⁷ each independently in each occurrencerepresents a hydrogen atom, a fluorine atom or a lower fluoroalkylgroup, and preferably a fluorine atom. The “lower fluoroalkyl group” is,for example, a fluoroalkyl group having 1 to 6 carbon atoms, preferably1 to 3 carbon atoms, preferably a perfluoroalkyl group having 1 to 3carbon atoms, more preferably a trifluoromethyl group orpentafluoroethyl group, and further preferably a trifluoromethyl group.

In another embodiment, examples of the groups represented by X¹, X³, X⁵,X⁷ and X⁹, the following groups are mentioned:

wherein

R⁴¹ each independently represents a hydrogen atom, a phenyl group, analkyl group having 1 to 6 carbon atoms or a C₁₋₆ alkoxy group, andpreferably a methyl group;

in a group represented by X¹, some of the groups represented by Trepresent the following groups to be bound to PFPE of the molecularbackbone:

—CH₂O(CH₂)₂—,

—CH₂O(CH₂)₃—,

—CF₂O(CH₂)₃—,

—(CH₂)₂—,

—(CH₂)₃—,

—(CH₂)₄—,

—CONH—(CH₂)₃—,

—CON(CH₃)—(CH₂)₃—,

—CON(Ph)-(CH₂)₃— (wherein Ph stands for phenyl) or

a group represented by:

wherein R⁴² each independently represents a hydrogen atom, a C₁₋₆ alkylgroup or a C₁₋₆ alkoxy group, preferably a methyl group or a methoxygroup, and more preferably a methyl group;

some of the other groups represented by T, each represent a carbon atomin groups (that is, formula (A1), (A2), (D1) and (D2)) opposite to PFPEof the molecular backbone, and a Si atom to be bound to A in the groupsrepresented by the following formulae (B1), (B2), (C₁) and (C₂) and—(CH₂)_(n″)— (n″ represents an integer of 2 to 6) in groups representedby (E1) and (E2)); and the remaining groups represented by T, ifpresent, each independently represent a methyl group, a phenyl group,C₁₋₆ alkoxy group, a radical scavenging group or a UV absorbing group.

The radical scavenging group is not limited as long as it can capture aradical generated by light irradiation, and, for example, residues of abenzophenone, a benzotriazole, a benzoate, a phenyl salicylate, crotonicacid, a malonate, an organo-acrylate, a hindered amine, a hinderedphenol or a triazine, is mentioned.

The UV absorbing group is not limited as long as it can absorbultraviolet rays, and, for example, a residue of a benzotriazole, ahydroxybenzophenone, an ester of a substituted and unsubstituted benzoicacid or salicylic acid compound, an acrylate or an alkoxy cinnamate, anoxamide, an oxanilide, a benzoxazinone or a benzoxazole, is mentioned.

In a preferable embodiment, as a preferable radical scavenging group orUV absorbing group, the groups represented by the following formulae arementioned.

In this embodiment, X¹, X³, X⁵, X⁷ and X⁹ each independently mayrepresent a 3 to 10 valent organic group.

The number average molecular weight of the reactive perfluoropolyethergroup-containing silane compound to be used in the present invention ispreferably 1,000 to 30,000, preferably 1,500 to 30,000, and morepreferably 2,000 to 10,000.

The degree of dispersion (weight average molecular weight/number averagemolecular weight (Mw/Mn)) of the reactive perfluoropolyethergroup-containing silane compound to be used in the present invention,although it is not limited, may be preferably 1.0 or more and 3.0 orless, more preferably 1.0 or more and 2.0, and further preferably 1.0 to1.5. If the degree of dispersion is controlled to be 3.0 or less, theuniformity of a film can be more improved. As the degree of dispersiondecreases, the uniformity of the film is (more) improved.

In the reactive perfluoropolyether group-containing silane compound tobe used in the present invention, the number average molecular weight ofa perfluoropolyether moiety (Rf—PFPE-moiety or —PFPE-moiety), althoughit is not limited, is preferably 500 to 30,000, preferably 1,000 to30,000, and more preferably 1,500 to 10,000.

In a preferable embodiment, the reactive perfluoropolyethergroup-containing compound may be a compound represented by the followingformula (A1), (A2), (B1), (B2), (C1), (C2), (D1) or (D2), a so-calledreactive perfluoropolyether group-containing silane compound. If thesilane compound is used, cycle characteristics can be (more) improved.In addition, adhesion of the film formed of the reactiveperfluoropolyether group-containing silane compound to an electrode canbe improved.

In an embodiment, the reactive perfluoropolyether group-containingcompound is a compound represented by formula (A1) or (A2).

In an embodiment, the reactive perfluoropolyether group-containingcompound is a compound represented by formula (B1) or (B2).

In an embodiment, the reactive perfluoropolyether group-containingcompound is a compound represented by formula (C1) or (C2).

In an embodiment, the reactive perfluoropolyether group-containingcompound is a compound represented by formula (D1) or (D2).

In an embodiment, the reactive perfluoropolyether group-containingcompound is a compound represented by formula (E1) or (E2).

Compounds represented by formulae (A1), (A2), (B1), (B2), (C₁), (C₂),(D1), (D2), (E1) and (E2) may be produced by methods known in the art.

As a method for forming a coating layer of a perfluoropolyethergroup-containing compound on the surface of an electrode, for example,there is a method of forming a coating layer by forming a film of areactive perfluoropolyether group-containing compound on an electrodematerial, and optionally subjecting the film to a post-treatment.

A film of a perfluoropolyether group-containing compound may be formedon an electrode material by a method of applying the reactiveperfluoropolyether group-containing compound to a surface of theelectrode material so as to cover the surface. As the coating method,although it is not limited, e.g., a wet coating method and a dry coatingmethod may be used.

The reactive perfluoropolyether group-containing compound may bedirectly applied or as a component of a composition prepared by mixingit with other components such as a solvent.

Examples of the solvent to be used in the composition include a C₅₋₁₂perfluoroaliphatic hydrocarbon (for example, perfluorohexane,perfluoromethylcyclohexane and perfluoro-1,3-dimethylcyclohexane); apolyfluoroaromatic hydrocarbon (for example,bis(trifluoromethyl)benzene); a polyfluoroaliphatic hydrocarbon (forexample, C₆F₁₃CH₂CH₃ (for example, ASAHI KLIN (registered trade mark)AC-6000, manufactured by Asahi Glass Co., Ltd., and1,1,2,2,3,3,4-heptafluorocyclopentane (for example, ZEORORA-H(registered trade mark) manufactured by ZEON CORPORATION)); ahydrofluorocarbon (HFC) (for example, 1,1,1,3,3-pentafluorobutane(HFC-365mfc)); a hydrochlorofluorocarbon (for example, HCFC-225 (ASAHIKLIN (registered trade mark) AK225)); and a hydrofluoroether (HFE) (forexample, an alkyl perfluoroalkylether (a perfluoroalkyl group and analkyl group may be linear or branched) such as perfluoropropyl methylether (C₃F₇OCH₃) (for example, Novec (trade name) 7000, manufactured bySUMITOMO 3M), perfluorobutyl methyl ether (C₄F₉OCH₃) (for example, Novec(trade name) 7100, manufactured by SUMITOMO 3M), perfluorobutyl ethylether (C₄F₉OC₂H₅) (for example, Novec (trade name) 7200, manufactured bySUMITOMO 3M), perfluorohexyl methyl ether (C₂F₅CF(OCH₃)C₃F₇) (forexample, Novec (trade name) 7300 manufactured by SUMITOMO 3M) orCF₃CH₂OCF₂CHF₂ (for example, ASAHI KLIN (registered trade mark) AE-3000,manufactured by Asahi Glass Co., Ltd.),1,2-dichloro-1,3,3,3-tetrafluoro-1-propene (for example, Vertrel(registered trade mark) Sion, manufactured by Du Pont-MitsuiFluorochemicals Co., Ltd.). These solvents may be used alone or as amixture prepared by mixing two or more solvents in combination. Tocontrol, e.g., solubility of a reactive perfluoropolyethergroup-containing silane compound, another solvent may be mixed.

The composition may contain other components. Examples of the componentsinclude, but are not limited to, a catalyst.

Examples of the catalyst include an acid (for example, acetic acid,trifluoroacetic acid), a base (for example, ammonia, triethylamine,diethylamine) and a transition metal (for example, Ti, Ni, Sn).

The catalyst promotes hydrolysis and dehydration condensation of areactive perfluoropolyether group-containing silane compound toaccelerate formation of the coating layer.

Examples of the wet coating method include dip coating, spin coating,flow coating, spray coating, roll coating, gravure coating and ananalogous method.

Examples of the dry coating method include a PVD method, a CVD methodand an analogous method. The PVD method refers to a method of forming athin film by heating a solid raw material in vacuum (vacuum deposition)or irradiating a solid raw material with high speed electrons and ions,thereby applying physical energy to atoms present in a solid surface tovaporize the atoms, which are allowed to recouple on an electrodematerial. Examples of the PVD method include, but are not limited to, adeposition method (usually, vacuum deposition method) and sputtering.Examples of the deposition method (usually, vacuum deposition method)include resistance heating, electron beam, high-frequency heating using,e.g., microwave and ion beam depositions, and analogous methods.Examples of the CVD method include plasma-CVD, optical CVD and thermalCVD, and analogous methods. Of them, a PVD method is preferable,particularly a deposition method, for example resistance heatingdeposition or electron beam deposition, is preferable, and electron beamdeposition is more preferable.

Coating may be carried out also by an atmospheric pressure plasmamethod.

Subsequently, the film is optionally subjected to post treatment. Thepost treatment, although it is not limited, may be e.g., heating,moisture supply or both of them.

The post treatment may be carried out for improving durability (byextension, improving cycle characteristics or storage stability of alithium ion secondary battery) of the coating layer; however, it shouldbe noted that post treatment is not an essential step. For example, thefilm after the reactive perfluoropolyether group-containing compound isapplied thereto, may be just allowed to stand still.

In the manner as mentioned above, a coating layer, i.e., a film of thereactive perfluoropolyether group-containing compound, is formed on theelectrode material.

The electrode of the present invention may be obtained by treating asurface of an electrode material with a reactive perfluoropolyethergroup-containing compound; or the electrode may be formed from a mixtureof a raw material for forming an electrode material and a reactiveperfluoropolyether group-containing compound.

The thickness of the coating layer, although it is not limited,preferably falls within the range of 0.1 to 50 nm, preferably 0.3 to 50nm, more preferably 0.5 to 30 nm, and further preferably 1 to 10 nm. Ifthe thickness is increased, contact between an electrode material andthe electrolyte can be more effectively inhibited, with the result thatthe function or electrical characteristics of an electrochemical devicecan be improved. In contrast, if the thickness is reduced, the distancebetween an active material and the electrolyte can be reduced, with theresult that capacity can be increased.

In a preferable embodiment, the coating layer is a monomolecular film.If the coating layer is a monomolecular film, a thinner and denser filmcan be obtained, with the result that not only improvement of electricalcharacteristics but also increase of capacity can be attained at ahigher level.

The electrode of the present invention contains a compound having aperfluoropolyether group. Because of this, if the electrode is used inan electrochemical device, the cycle capacity retention rate of theelectrochemical device is improved and the resistance increase ratethereof can be suppressed, and further, deterioration in performanceduring storage at a high temperature can be suppressed. Although thepresent invention is not constrained by any theory, the reason why theaforementioned effect can be obtained is considered that direct contactbetween an electrode material and an electrolytic solution can besuppressed by a compound having a perfluoropolyether group contained inthe electrode of the present invention.

Electrode Material

The electrode material refers to a member constituting a main part of anelectrode of an electrochemical device and ordinarily used in variouselectrochemical devices. The electrode material may be appropriatelyselected by those skilled in the art in accordance with the type ofelectrochemical device. For example, in an alkali metal ion battery, theelectrode material may be an active material-containing portioncontaining an active material (hereinafter, used for collectivelyreferring to a positive electrode active material and a negativeelectrode active material). In an electric double-layer capacitor, theelectrode material may be a portion forming an electric-double layer atthe interface in contact with an electrolyte, for example, a portioncontaining carbon or graphite.

The electrode of the present invention may be used as either one of apositive electrode and a negative electrode in an electrochemicaldevice. If the electrode of the present invention is used as thepositive electrode, oxidative decomposition of an electrolytic solutioncan be suppressed, with the result that deterioration of theelectrochemical device (battery) and decomposition of the structure ofthe positive electrode due to decomposition of the electrolytic solutioncan be suppressed. If the electrode of the present invention is used asthe negative electrode, a solid/electrolyte interface (SEI) structure,which is formed at the interface between the electrode and theelectrolytic solution, can be stabilized to allow lithium ions tosatisfactorily move. As a result, an increase of resistance can besuppressed.

Since the electrode of the present invention contains aperfluoropolyether group-containing compound in the surface thereof, asmentioned above, if the electrode is used as a positive electrode and/ora negative electrode in an electrochemical device, satisfactoryelectrical characteristics and large capacity of the electrochemicaldevice can be achieved.

<Electrochemical Device>

As mentioned above, the electrode of the present invention can be usedin various electrochemical devices.

Accordingly, the present invention also provides electrochemical deviceshaving the electrode of the present invention.

The electrochemical device refers to a device having at least a pair ofelectrodes and an electrolyte intervening between the pair ofelectrodes.

Examples of the electrochemical device include, but are not limited to,a battery, an electrochemical sensor, an electrochromic device, anelectrochemical switching device, an electrolytic capacitor and anelectrochemical capacitor.

The battery is not limited as long as it has electrodes and anelectrolyte. Examples thereof include an alkali metal battery, an alkalimetal ion battery, an alkaline earth metal ion battery, a radicalbattery, a solar cell and a fuel cell. In a preferable embodiment, asspecific examples of the battery, an alkali metal battery, an alkalimetal ion battery or an alkaline earth metal battery such as a lithiumbattery, a lithium ion battery, a sodium ion battery, a magnesiumbattery, a lithium air battery, a sodium-sulfur battery and alithium-sulfur battery can be mentioned, and preferably a lithium ionbattery can be mentioned. The battery may be a primary battery and asecondary battery, preferably an alkali metal ion secondary battery, andparticularly, a lithium ion secondary battery.

The electrochemical sensor refers to a sensor, which is used fordetecting or determining natural phenomena or mechanical,electromagnetic, thermal, acoustical and chemical properties of anartifact, or spatial information/timing information indicated by them,and which has an electrode(s) using an electrochemical principle and anelectrolyte. Examples of the electrochemical sensor include an actuator,a humidity sensor, a gas-concentration sensor, an ion-concentrationsensor and an odor sensor.

The electrochromic device refers to a device, which controls opticalabsorption in a reversible manner by application of voltage (orcurrent), and which has an electrode(s) using an electrochemicalreaction and an electrolyte. Examples of the electrochromic deviceinclude an electrochromic device electrically changing color.

The electrochemical switching device is not limited as long as it has anelectrode(s) and an electrolyte. Examples thereof include anelectrochemical transistor and a field effect transistor.

The electrolytic capacitor is not limited as long as it has anelectrode(s) and an electrolyte. Examples thereof include an aluminumelectrolytic capacitor and a tantalum electrolytic capacitor.

The electrochemical capacitor is not limited as long as it has anelectrode(s) and an electrolyte. Examples thereof include an electricdouble layer capacitor, a redox capacitor and a hybrid capacitor such asa lithium ion capacitor.

In an embodiment, the electrochemical device of the present inventioncan be a device using the electrode of the present invention only as oneof the electrodes. For example, the electrochemical device of thepresent invention can employ the electrode of the present invention onlyas a negative electrode or a positive electrode. In an embodiment, theelectrochemical device of the present invention can employ the electrodeof the present invention only as a positive electrode. In anotherembodiment, the electrochemical device of the present invention canemploy the electrode of the present invention as both electrodes, i.e.,a positive electrode and a negative electrode.

The electrochemical device of the present invention is not limited bythe examples mentioned above as long as it is a device consisting of atleast a pair of electrodes and an electrolyte intervening between theelectrodes. Also, the electrochemical device of the present invention issatisfactory if the electrode of the present invention is used as atleast one of the electrodes and other constituents may be the same as ina conventional electrochemical device unless otherwise specified.

<Alkali Metal Ion Secondary Battery>

Now, the electrochemical device of the present invention will be morespecifically described by way of an alkali metal ion secondary batteryas an example.

In an embodiment, the present invention provides an alkali metal ionsecondary battery having the electrode of the present invention as atleast one of the positive electrode and negative electrode andpreferably a lithium ion secondary battery.

The alkali metal ion secondary battery of the present invention possiblyhas a general structure as an alkali metal ion secondary battery. Forexample, the alkali metal ion secondary battery of the present inventionpossibly has, e.g., a positive electrode, a negative electrode, aseparator and an electrolytic solution in an exterior case. Also, thealkali metal ion secondary battery of the present invention furtherpossibly has members except those mentioned above such as a positiveelectrode current collector tab, a negative electrode current collectortab and a battery cover, or a member for protecting the battery, such asan internal pressure release valve or a PTC element.

In the alkali metal ion secondary battery, an electrode material may bean active material-containing portion containing an active material(hereinafter, used for collectively referring to a positive electrodeactive material and a negative electrode active material). Typically, anelectrode material may be constituted of an active material-containingportion and a current collector. In an embodiment, the activematerial-containing portion is present on the current collector in theform of a laminate.

Positive Electrode

The positive electrode has a positive electrode material containing anactive material-containing portion containing a positive electrodeactive material. If the positive electrode is the electrode of thepresent invention, the positive electrode (further) has aperfluoropolyether group-containing compound on a surface of thepositive electrode material.

The positive electrode active material is not limited as long as it canelectrochemically absorb/desorb an alkali metal ion; preferably, forexample, a substance containing an alkali metal and at least onetransition metal. Specific examples thereof include an alkalimetal-containing transition metal composite oxide and an alkalimetal-containing transition metal phosphate compound. Of them, an alkalimetal-containing transition metal composite oxide generating highvoltage is particularly preferable as the positive electrode activematerial. Examples of the alkali metal ion include a lithium ion, asodium ion and a potassium ion. In a preferable embodiment, the alkalimetal ion may be a lithium ion. That is, in this embodiment, the alkalimetal ion secondary battery refers to a lithium ion secondary battery.

Examples of the alkali metal-containing transition metal composite oxideinclude a lithium-manganese spinel composite oxide represented byformula:M_(a)Mn_(2-b)M¹ _(b)O₄wherein M represents at least one metal selected from Li, Na and K;0.9≤a; 0≤b≤1.5; M¹ is at least one metal selected from the groupconsisting of Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga,In, Si and Ge;a lithium-nickel composite oxide represented by formula:MNi_(1-c)M² _(c)O₂wherein M is at least one meal selected from Li, Na and K; 0≤c≤0.5; M²represents at least one metal selected from the group consisting of Fe,Co, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge;and,a lithium-cobalt composite oxide represented by formula:MCo_(1-d)M³ _(d)O₂wherein M is at least one meal selected from Li, Na and K; 0≤d≤0.5; M³represents at least one metal selected from the group consisting of Fe,Ni, Mn, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge.

In the above, M is preferably at least one meal selected from Li, Na andK, more preferably Li or Na, and further preferably Li.

Of them, for the reason that an alkali metal ion secondary batteryhaving a high energy density and a high power can be provided, MCoO₂,MMnO₂, MNiO₂, MMn₂O₄, MNi_(0.8)Co_(0.15)Al_(0.05)O₂ orMNi_(1/3)Co_(1/3)Mn_(1/3)O₂ is preferable.

Examples of other positive electrode active materials include MFePO₄,MNi_(0.8)Co_(0.2)O₂, M_(1.2)Fe_(0.4)Mn_(0.4)O₂, MNi_(0.5)Mn_(1.5)O₂,MV₃O₆ and M₂MnO₃. Particularly, a positive electrode active materialsuch as M₂MnO₃ and MNi_(0.5)Mn_(1.5)O₂ is preferable because even if thelithium ion secondary battery using such a positive electrode isoperated at a voltage beyond 4.4 V, e.g., a voltage of, 4.6 V or more,its crystal structure is not broken. Accordingly, an electrochemicaldevice, such as a lithium ion secondary battery, having the positiveelectrode of the present invention using a positive electrode materialcontaining a positive electrode active material as mentioned above, ispreferable because even if it is stored at a high temperature, theresidual capacity of the battery rarely decreases and the resistanceincrease rate rarely changes, and even if it is operated at a highvoltage, the battery performance rarely deteriorates.

Negative Electrode

The negative electrode has a negative electrode material containing anactive material-containing portion containing a negative electrodeactive material. If the negative electrode is the electrode of thepresent invention, the negative electrode (further) has aperfluoropolyether group-containing compound on a surface of thenegative electrode material.

Examples of the negative electrode active material that can be mentionedinclude thermolysis products of an organic substance in various thermaldecomposition conditions, carbonaceous materials that can absorb/desorbalkali metals, preferably lithium, such as artificial graphite andnatural graphite, metal oxide materials that can absorb/desorb an alkalimetal, such as stannum oxide and silicon oxide; alkali metals; alkalimetal alloys; and alkali metal-containing metal composite oxidematerials. These negative electrode active materials may be used as amixture (two or more).

As the carbonaceous material that can absorb/desorb an alkali metal,artificial graphite or purified natural graphite produced by treatinggraphitizable pitch, which can be obtained from various materials, at ahigh temperature, or a material obtained by treating the surface ofgraphite with pitch or an organic substance except the pitch, followedby carbonizing it, is preferable; and a material selected fromcarbonaceous materials obtained by subjecting natural graphite,artificial graphite, an artificial carbonaceous material and anartificial graphite substance once or more to a heat treatment performedin the range of 400 to 3200° C.; a carbonaceous material where anegative electrode active material layer is constituted of carbonaceoussubstances having at least two types or more different crystallinitiesand/or having an interface at which the different crystallinitycarbonaceous substances are in contact with each other; and acarbonaceous material where a negative electrode active material layerhas an interface at which at least two types of carbonaceous substancesdifferent in orientation are in contact with each other, is morepreferable because the initial irreversible capacity, high currentdensity charge and discharge characteristics are well balanced. Thesecarbon materials may be used alone or in combination (two types or morecan be used in any combination and any ratio).

Examples of the carbonaceous material obtained by subjecting anartificial carbonaceous material and an artificial graphite material,once or more, to a heat treatment performed in the range of 400 to 3200°C. include coal-based coke, petroleum coke, coal pitch, petroleum-basedpitch, and products obtained by oxidation treatment of these; needlecoke, pitch coke and carbon agents obtained by partial graphitization ofthese; furnace black, acetylene black, a thermolysis product of anorganic substance such as a pitch-based carbon fiber; organic substancesthat can be carbonized and carbides of these or solutions of the organicsubstances that can be carbonized dissolved in low molecular weightorganic solvents such as benzene, toluene, xylene, quinoline andn-hexane, and carbides of these.

As the metal material to be used as the negative electrode activematerial, a single alkali metal, a single metal or an alloy forming analkali metal alloy or oxides, carbides, nitrides, silicides, sulfides orphosphides of these may be mentioned, as long as it can absorb/desorb analkali metal. As the single metal or alloy forming an alkali metalalloy, a material containing a metal/metalloid element belonging to the13rd and 14th families is preferable, and a single metal such asaluminum, silicon and stannum (hereinafter, simply referred to as“predetermined metal elements”) and alloys or compounds containing theseatomic elements are more preferable. These may be used alone or in anycombination of two or more at any ratio.

Examples of a negative electrode active material having at least oneatomic element selected from the predetermined metal elements include asingle metal of any one of the predetermined metal elements; an alloyformed of two types or more predetermined metal elements; an alloyformed of a single or two types or more predetermined metal elements anda single or two types or more metal elements except the predeterminedmetal elements; (and) a compound containing a single or two types ormore predetermined metal elements; and composite compounds such as anoxide, a carbide, a nitride, a silicide, a sulfide or a phosphide of thecompound. If a single metal substance, an alloy or a metal compound asmentioned above is used as the negative electrode active substance, thecapacity of the resultant battery can be increased.

In addition, compounds obtained by complexly binding these compositecompounds to several elements such as single metals, an alloy ornonmetal elements, are mentioned; more specifically, if silicon andstannum are used, alloys of these elements with a metal not serving as anegative electrode, can be used. For example, in the case of usingstannum, a complicated compound containing 5 to 6 elements, morespecifically, containing a metal serving as a negative electrode exceptstannum and silicon, a metal not serving as a negative electrode, andnon-metal elements in combination, can be used.

More specifically, Si, SiB₄, SiB₆, Mg₂Si, Ni₂Si, TiSi₂, MoSi₂, CoSi₂,NiSi₂, CaSi₂, CrSi₂, Cu₆Si, FeSi₂, MnSi₂, NbSi₂, TaSi₂, VSi₂, WSi₂,ZnSi₂, SiC, Si₃N₄, Si₂N₂O, SiO_(v) (0<v≤2), LiSiO or stannum, SnSiO₃,LiSnO, Mg₂Sn and SnO_(w) (0<w≤2) is mentioned.

A composite material containing Si or Sn as a first constituent elementand further containing second and third constituent elements ismentioned. The second constituent element is at least one element of,e.g., cobalt, iron, magnesium, titanium, vanadium, chromium, manganese,nickel, copper, zinc, gallium and zirconium. The third constituentelement is at least one element of, e.g., boron, carbon, aluminum andphosphorus.

In particular, for the reason that high battery capacity and excellentbattery characteristics can be obtained, a single silicon or stannum(trace amounts of impurities may be contained), SiO_(v) (0<v≤2), SnO_(w)(0≤w≤2), a Si—Co—C composite material, a Si—Ni—C composite material, aSn—Co—C composite material and a Sn—Ni—C composite material arepreferable as the metal material.

The alkali metal-containing metal composite oxide material to be used asthe negative electrode active material is not limited as long as it canabsorb/desorb an alkali metal. In consideration of high current densitycharge and discharge characteristics, a material containing titanium andan alkali metal is preferable; an alkali metal-containing compositemetal oxide material containing titanium is more preferable; and acomposite oxide containing an alkali metal and titanium (hereinaftersimply referred to as “alkali metal/titanium composite oxide”) isfurther preferable. In short, it is particularly preferable that analkali metal titanium composite oxide having a spinel structure is addedto a negative electrode active material for a battery using anelectrolytic solution, because output resistance is greatly reduced.

As the alkali metal titanium composite oxide, it is preferable to use acompound represented by formula:M_(x)Ti_(y)M³ _(z)O₄wherein M represents at least one metal selected from Li, Na and K; andM³ represents at least one element selected from the group consisting ofNa, K, Co, Al, Fe, Ti, Mg, Cr, Ga, Cu, Zn and Nb.

In the above, M is preferably a metal selected from Li, Na and K, morepreferably Li or Na, and further preferably Li.

Of the compounds mentioned above, a compound satisfying the followingcompositional conditions:1.2≤x≤1.4,1.5≤y≤1.7,z=0  (i)0.9≤x≤1.1,1.9≤y≤2.1,z=0, and/or  (ii)0.7≤x≤0.9,2.1≤y≤2.3,z=0  (iii)are/is particularly preferable because well-balanced battery performanceis obtained.

A particularly preferable composition of the above compound satisfyingcondition (i) is M_(4/3)Ti_(5/3)O₄; the composition satisfying condition(ii) is M₁Ti₂O₄; and the composition satisfying condition (iii) isM_(4/5)Ti_(11/5)O₄. As a structure of a case satisfying, Z≠0, forexample, M_(4/3)Ti_(4/3)Al_(1/3)O₄ is preferable.

An active material-containing portion containing a negative electrodeactive material as mentioned above is preferably formed of anegative-electrode mixture containing the negative electrode activematerial and can be obtained, for example, by applying thenegative-electrode mixture onto a current collector followed by dryingit.

It is preferable that the negative-electrode mixture further contains abinding agent, a thickener and a conductive material.

The Electrode of the Present Invention in Alkali Metal Ion SecondaryBattery

In the alkali metal ion secondary battery, the electrode of the presentinvention is used as at least one of the electrodes.

If the electrode of the present invention is used as the positiveelectrode, oxidative decomposition of the electrolytic solution can besuppressed, with the result that deterioration of the battery anddecomposition of a positive electrode structure caused by decompositionof the electrolytic solution can be suppressed. If the electrode of thepresent invention is used as the negative electrode, a solid electrolyteinterface (SEI) structure formed at the interface between the electrodeand the electrolytic solution, can be stabilized, attaining satisfactorymovement of lithium ions, thereby suppressing an increase of resistance.

The electrode of the present invention used in an alkali metal ionsecondary battery contains a perfluoropolyether group-containingcompound preferably on an electrode material, and more specifically, onan active material-containing portion.

In an embodiment of the alkali metal ion secondary battery of thepresent invention, the electrode of the present invention is used onlyas the positive electrode. If the electrode of the present invention isused only as the positive electrode, oxidative decomposition of theelectrolytic solution can be suppressed, and deterioration of thebattery and decomposition of a positive electrode structure can besuppressed. The effect is further exerted in a battery to be operated ata higher voltage.

In another embodiment of the alkali metal ion secondary battery of thepresent invention, the electrode of the present invention is used onlyas the negative electrode. If the electrode of the present invention isused only as the negative electrode, a solid electrolyte interface (SEI)structure formed at the interface between the electrode and theelectrolytic solution can be stabilized, with the result that reductivedecomposition of the electrolytic solution can be suppressed up to acertain level and an increase of resistance of an SEI film can besuppressed.

In another embodiment of the alkali metal ion secondary battery of thepresent invention, the electrode of the present invention is used asboth the positive electrode and the negative electrode. If the electrodeof the present invention is used as both the positive electrode andnegative electrode, oxidative decomposition of the electrolytic solutioncan be suppressed and further a solid electrolyte interface (SEI)structure formed at the interface between the electrode and theelectrolytic solution can be stabilized.

If the electrode of the present invention is used as the positiveelectrode, in other words, if a perfluoropolyether group-containingcompound is present in the positive electrode, oxidative decompositionof the electrolytic solution is suppressed particularly during ahigh-voltage operation time and deterioration of the battery can besuppressed. In addition, the residual capacity rate of the battery isimproved.

The electrode of the present invention to be used as the positiveelectrode and/or a negative electrode of an alkali metal ion secondarybattery may be produced by treating the surface of an electrode materialcoated with an active material, with a reactive perfluoropolyethergroup-containing compound, or produced by applying an electrode mixturecontaining the reactive perfluoropolyether group-containing compound ina step of forming a coating layer of the electrode mixture.

Since the electrode of the present invention contains aperfluoropolyether group-containing compound in the surface, asmentioned above, if the electrode is used as the positive electrodeand/or negative electrode of an alkali metal ion secondary battery,preferably a lithium ion secondary battery, the alkali metal ionsecondary battery can acquire satisfactory cycle characteristics, alarge battery capacity, and satisfactory storage characteristics.

Separator

The separator is used for separating the positive electrode and thenegative electrode to prevent a current short circuit caused by contactof both electrodes; at the same time, passing alkali metal ions,preferably lithium ions therethrough. The separator may be a porous filmformed of, for example, a synthetic resin or ceramic, or a laminatedfilm formed by laminating at least two types of porous films. As thesynthetic resin, for example, polytetrafluoroethylene, polypropylene orpolyethylene is mentioned.

Electrolytic Solution

The positive electrode, negative electrode and separator are impregnatedwith preferably, a liquid electrolyte, i.e., an electrolytic solution.The electrolytic solution is obtained by dissolving an electrolyte saltin a solvent, and optionally contains substances other than theelectrolyte such as additives.

The solvent may be any one of nonaqueous solvents such as organicsolvents or a mixture of at least two types of nonaqueous solvents.

As the solvent, for example, ethylene carbonate, propylene carbonate,butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methylcarbonate, methyl propyl carbonate, γ-butyrolactone, γ-valerolactone,1,2-dimethoxyethane or tetrahydrofuran is mentioned. Specific examplesthereof include 2-methyl tetrahydrofuran, tetrahydropyran,1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane or 1,4-dioxane,methyl acetate, ethyl acetate, methyl propionate, ethyl propionate,methyl butyrate, methyl isobutyrate, methyl trimethylacetate or ethyltrimethylacetate, acetonitrile, glutaronitrile, adiponitrile,methoxyacetonitrile, 3-methoxypropionitrile, N,N-dimethylformamide,N-methylpyrrolidinone, N-methyloxazolidinone,N,N′-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane,trimethyl phosphate and dimethylsulfoxide. If a solvent(s) as mentionedabove is used, e.g., excellent battery capacity, cycle characteristicsand storage characteristics can be obtained.

Of the solvents, at least one of ethylene carbonate, propylenecarbonate, dimethyl carbonate, diethyl carbonate and ethyl methylcarbonate is preferably used. If such a solvent is used, more excellentcharacteristic can be obtained. In this case, a combination of ahigh-viscosity (high electric permittivity) solvent (for example,relative electric permittivity ε≥30) such as ethylene carbonate orpropylene carbonate and a low-viscosity solvent (for example, viscosity≤1 mPa·s) such as dimethyl carbonate, ethyl methyl carbonate or diethylcarbonate, is more preferably used. If these solvents are used incombination, dissociation of an electrolyte salt and ion mobility areimproved.

In particular, a solvent as mentioned above preferably contains anunsaturated carbon bond cyclic carbonate. If a solvent contains anunsaturated carbon bond cyclic carbonate, a stable protective film isformed on the surface of a negative electrode during a charge/dischargetime, suppressing the decomposition reaction of an electrolyticsolution. The unsaturated carbon bond cyclic carbonate refers to acyclic carbonate having one or two or more unsaturated carbon bonds,such as vinylene carbonate or vinylethylene carbonate. Note that, thecontent of the unsaturated carbon bond cyclic carbonate in a solvent,although it is not limited, is, for example, 0.01 wt % or more and 10 wt% or less. If the content of the unsaturated carbon bond cycliccarbonate in a solvent falls within the range mentioned above, thedecomposition reaction of the electrolytic solution can be suppressedwithout reducing a battery capacity.

A solvent as mentioned above preferably contains at least one of ahalogenated linear carbonate and a halogenated cyclic carbonate. If sucha solvent is contained, a stable protective film is formed on thesurface of a negative electrode during a charge/discharge time,suppressing the decomposition reaction of an electrolytic solution. Thehalogenated linear carbonate refers to a linear carbonate having one ortwo or more halogen groups. The halogenated cyclic carbonate refers to acyclic carbonate having one or two or more halogen groups. The type ofthe halogen group is not limited. Of the halogen groups, a fluorinegroup, a chlorine group or a bromine group is preferable and a fluorinegroup is more preferable. If a halogen group as mentioned above is used,a higher effect can be obtained. Note that, the number of halogen groupsis preferably two rather than one, and may be three or more. If thenumber of halogen groups increases, a firmer and more stable protectivefilm is obtained. Because of this, the decomposition reaction of anelectrolytic solution is more suppressed. The halogenated linearcarbonate is, for example, fluoromethyl methyl carbonate,bis(fluoromethyl) carbonate or difluoromethy methyl carbonate. Thehalogenated cyclic carbonate is, for example,4-fluoro-1,3-dioxolan-2-one or 4,5-difluoro-1,3-dioxolan-2-one. Notethat, the contents of halogenated linear carbonate and halogenatedcyclic carbonate in a solvent, although they are not limited, are, forexample, 0.01 wt % or more and 50 wt % or less. If the contents fallwithin the range, the decomposition reaction of an electrolytic solutionis more suppressed without excessively reducing a battery capacity.

A solvent as mentioned above may contain sultone (cyclic sulfonate). Ifa solvent contains sultone (cyclic sulfonate), chemical stability of anelectrolytic solution can be more improved. Sultone is, for example,propane sultone or propene sultone. Note that, the content of a sultonein the solvent, although it is not limited, is, for example, 0.5 wt % ormore and 5 wt % or less. If the content falls within the range, areduction of a battery capacity can be suppressed and the decompositionreaction of an electrolytic solution can be suppressed.

A solvent as mentioned above may contain an acid anhydride. If a solventcontains an acid anhydride, chemical stability of an electrolyticsolution is more improved. The acid anhydride is, for example,dicarboxylic anhydride, disulfonic acid anhydride or carboxylic acidsulfonic acid anhydride. The dicarboxylic anhydride is, for example,succinic anhydride, glutaric anhydride or maleic anhydride. Thedisulfonic acid anhydride is, for example, ethane disulfonic anhydrideor propane disulfonic anhydride. The carboxylic acid sulfonic acidanhydride is, for example, anhydrous sulfobenzoic acid, anhydroussulfopropionic acid or anhydrous sulfobutyric acid. Note that, thecontent of an acid anhydride in a solvent, although it is not limited,is, for example, 0.5 wt % or more and 5 wt % or less. If the contentfalls within the range, a reduction of a battery capacity can besuppressed and the decomposition reaction of an electrolytic solutioncan be suppressed.

Electrolyte Salt

The electrolyte salt may contain any one or two types or more of alkalimetal salts as described below. Note that, the electrolyte salt may be asalt other than an alkali metal salt (for example, a light metal saltother than an alkali metal salt).

Examples of the alkali metal salt include compounds such as MPF₆, MBF₄,MClO₄, MAsF₆, MB (C₆H₅)₄, MCH₃SO₃, MCF₃SO₃, MAlCl₄, M₂SiF₆, MCl and MBr,wherein M represents at least one metal selected from Li, Na and K,preferably a metal selected from Li, Na and K, more preferably Li or Na,and further preferably Li.

If such an alkali metal salt is used, e.g., an excellent batterycapacity, cycle characteristics and storage characteristics can beobtained. In particular, at least one selected from MPF₆, MBF₄, MClO₄and MAsF₆ is preferable and MPF₆ is more preferable. If such an alkalimetal salt is used, internal resistance further decreases and a highereffect can be obtained.

The content of an electrolyte salt as mentioned above relative to asolvent is preferably 0.1 mol/kg or more and 3.0 mol/kg or less. This isbecause if the content falls within the range, high ion conductivity canbe obtained.

<Battery Design>

The structure of the electrodes may be either one of a laminatedstructure constructed by stacking a positive-electrode plate and anegative-electrode plate with a separator interposed between them and aroll structure constructed by winding a laminate obtained by stacking apositive-electrode plate and a negative-electrode plate with a separatorinterposed between them, like a coil. The volume ratio of the electrodegroups occupied in the battery internal volume (hereinafter referred toas “an electrode group occupancy”) is usually 40% or more, preferably50% or more; and usually 90% or less and preferably 80% or less.

If the electrode group occupancy is below the range, battery capacity islow. In contrast, if the electrode group occupancy exceeds the range,the void space becomes low. In this case, if the temperature of thebattery increases, members expand or the vapor pressure of liquidcomponent of an electrolyte increases, increasing internal pressure. Asa result, the charge and discharge repeatability of the battery andcharacteristics such as high temperature storage stability deteriorateand, in some cases, further a gas release valve for releasing internalpressure is actuated.

The structure of the current collector is not limited. To effectivelyimprove charge and discharge characteristics at a high current densityby the electrolytic solution, it is preferable to form a structurehaving wiring and joining parts reduced in resistance.

If the electrodes are laminated, it is suitable to use a structureformed by bundling the metal core portions of individual electrodelayers and fixing the bundle to a terminal by welding. If a singleelectrode area is large, since the internal resistance increases, aplurality of terminals are provided within the electrode to reduceresistance. If the electrodes are wound like a coil, the internalresistance can be reduced by providing a plurality of lead-likestructures in the positive electrodes and negative electrodes andbundling them and fixing the bundle to a terminal.

The material for an exterior case is not limited as long as it is asubstance stable to the electrolytic solution to be used. Morespecifically, a metal such as a nickel plated steel sheet, stainlesssteel, aluminum or an aluminum alloy or a magnesium alloy or a laminatedfilm (laminate film) of a resin and an aluminum foil, is used. To reduceweight, a metal such as aluminum or an aluminum alloy or a laminate filmcan be suitably used.

In the exterior case made of metals, metals are mutually welded by laserwelding, resistance welding or ultrasonic welding to form a hermeticallysealed structure or a structure formed of the metals by caulking via aresin gasket. In the exterior case made of a laminate film as mentionedabove, resin layers are heat-sealed to obtain a hermetically sealedstructure. To improve sealability, a resin different in type from theresin used in the laminate film may be interposed between the resinlayers. Particularly, when a sealed structure is formed by heat-sealingof resin layers via a current collector terminal, a metal and a resinare joined. For the reason, a resin having a polar group and a resinmodified by introducing a polar group therein are suitably used as theresin to be interposed.

The shape of the alkali metal ion secondary battery of the presentinvention can be arbitrarily selected. For example, a cylindrical type,a square shape, a laminate and a coin (these may be large in size) arementioned. Note that, the shapes and structure of the positiveelectrode, negative electrode and separator to be used may be changeddepending on the shape of a battery.

<Electronics and Module>

An electrochemical device as mentioned above can be used in variouselectronics or modules. Accordingly, the present invention provideselectrochemical devices of the present invention, particularly anelectronic device or a module having a lithium ion secondary battery.

EXAMPLES

Now, the present invention will be described by way of Examples;however, the present invention is not limited to these Examples alone.

(Preparation of Electrolytic Solution)

Ethylene carbonate as a high-permittivity solvent and ethyl methylcarbonate as a low-viscosity solvent were mixed so as to satisfy avolume ratio 30 to 70. To the solvent mixture, LiPF₆ was added so as toobtain a concentration of 1.0 mole/liter to obtain a nonaqueouselectrolytic solution.

(Production of Lithium Ion Secondary Battery)

LiNi_(1/3)Mn_(1/3)Co_(1/3)O₂ was used as a positive electrode activematerial. Carbon black was used as a conductive material. A dispersionof polyvinylidene fluoride (PVdF) in N-methyl-2-pyrrolidone was used asa binding agent. The active material, conductive material and bindingagent were mixed so as to satisfy a solid content ratio of 92/3/5 (mass% ratio) to prepare a slurry-state positive-electrode mixture. Theslurry-state positive-electrode mixture obtained was uniformly appliedto an aluminum-foil current collector having a thickness of 20 μm, driedand compression-molded by a press machine to obtain a positive electrodelaminate. The positive electrode laminate was punched by a punchingmachine to obtain circular positive electrode materials having adiameter of 1.6 cm.

An artificial graphite powder and amorphous silicon (SiO) were used as anegative electrode active material. An aqueous dispersion of sodiumcarboxylmethyl cellulose (the concentration of sodium carboxymethylcellulose: 1 mass %) was used as a thickener. An aqueous dispersion of astyrene-butadiene rubber (styrene-butadiene rubber concentration 50 mass%) was used as a binding agent. The active material, thickener andbinding agent were mixed so as to satisfy a solid content ratio of93/4.6/1.2/1.2 (mass % ratio) to prepare a slurry-statenegative-electrode mixture. The slurry-state negative-electrode mixtureobtained was uniformly applied to a copper foil having a thickness of 20μm, dried and compression-molded by a press machine to obtain a negativeelectrode. The negative electrode was punched by a punching machine toobtain circular negative electrode materials having a diameter of 1.6cm.

The positive electrode material and negative electrode material obtainedabove were subjected to a coating treatment with each of the compoundsshown in Table 1 below and the treatment was performed in the followingmanner.

Coating Treatment (Dip Method)

The following fluorine compounds (compounds 1 to 5) were each dilutedwith hydrofluoroether (HFE7200, manufactured by SUMITOMO 3M) so as tosatisfy a solid content of 0.1%. After an electrode material was dippedin the diluted solution for one minute, excessive compound present onthe surface of the electrode material was washed away with HFE7200.Thereafter, the electrode material was dried to obtain an electrodehaving the surface treated with the fluorine compound.

Treatment with Coating Agent (Physical Vapor Deposition (PVD) Method)

The following fluorine compounds (compounds 1 to 5) were each weighedand put in a copper container, which was set in a resistance heatingvessel in the vacuum chamber; and an electrode material was set in anupper portion of the chamber. Thereafter, the internal pressure of thechamber was controlled to be 10⁻³ Pay by a vacuum pump. The resistanceheating of the compound in the copper container was carried out todeposit the compound onto the electrode material. In this manner, anelectrode whose surface was treated with the compound was obtained. Notethat, if the compound was applied with a throughput of 50 mg (in termsof solid content) per m² (0.01 mg per a single electrode sheet), a filmthickness of 9 to 10 nm can be obtained. The film thickness is definedas a film thickness measured by a crystal oscillator set in the vapordeposition chamber.

Compound 1 (PFPE-Si):

CF₃CF₂CF₂O—(CF₂CF₂CF₂O)_(n)—CF₂CF₂ (CH₂CH (Si(OMe)₃))_(n)—H, wherein nused in the portion “CF₃CF₂CF₂O—(CF₂CF₂CF₂O)_(n)—CF₂CF₂” represents 25.

Compound 2 (PFPE-OH):

CF₃CF₂CF₂O—(CF₂CF₂CF₂O)_(n)—CF₂CF₂CF₂OH, wherein n=25

Compound 3 (PFPE-COOH):

CF₃CF₂CF₂O—(CF₂CF₂CF₂O)_(n)—CF₂CF₂CF₂COOH wherein n=25

Compound 4:

CF₃CF₂CF₂O—(CF₂CF₂CF₂O)_(n)—CF₃ wherein n=25

Compound 5:

CF₃CF₂CF₂CF₂CF₂CF₂CH₂CH₂—Si(OMe)₃

The circular positive electrode and negative electrode were allowed toface each other with a microporous polyethylene film (separator) havinga thickness 20 μm interposed between them, and then, the nonaqueouselectrolytic solution obtained above was poured. After the electrodesand separator were sufficiently impregnated with the electrolyticsolution, they were sealed, preliminarily charged and allowed to standstill (for aging) to form a coin-type lithium ion secondary battery.

(Determination of Battery Characteristics)

The cycle capacity retention rates and resistance increase rates of thecoin-type lithium ion secondary batteries obtained in this manner werechecked.

(Cycle Capacity Retention Rate)

The secondary batteries produced above were charged with a currentcorresponding to 0.5 C up to 4.2 V (refers to constant current/constantvoltage charging (hereinafter referred to as “CC/CV charging”) (0.1 Ccut)) at 25° C.; thereafter discharged with a constant current of 0.5 Cup to 3 V. This operation was defined as a single cycle. The initialdischarge capacity was obtained from the discharge capacity at the firstcycle. The unit 1 C herein represents a current value required fordischarging the reference capacity of a battery in one hour. Forexample, 0.5 C represents ½ of the current value. The batteries werecharged again up to 4.2 V in accordance with the CC/CV charging (0.1 Ccut) and then, charge and discharge were carried out in the same manneras above. After 200 cycles, the discharge capacity was measured. Theratio of the discharge capacity after 200 cycles relative to the initialdischarge capacity was obtained based on the following expression andspecified as a cycle capacity retention rate (%). The measurementtemperature was set to be 60° C. The results are shown in Table 1 below.(Discharge capacity after 200 cycles)/(Initial dischargecapacity)×100=Cycle capacity retention rate (%)

(Resistance Increase Rate)

A charge and discharge cycle performed in predetermined conditions(charged at 0.5 C under a predetermined voltage until the chargingcurrent became 0.1 C and discharged at a current equivalent to 1 C up to3.0 V) was defined as a single cycle. The resistance after 3 cycles andthe resistance after 200 cycles were measured. The measurementtemperature was set to be 25° C. A resistance increase rate was obtainedbased on the following expression. The results are shown in Table 1.Resistance increase rate (%)=Resistance after 200 cycles (Ω)/Resistance(Ω) after 3 cycles×100

TABLE 1 Compound for coating Cycle Treatment capacity ResistancePositive method Negative Treatment retention rate increase rateelectrode (throughput) electrode method (%) (%) Example 1 Compound PVDCompound PVD 95 132 1 (0.01 mg) 1  (0.01 mg) Example 2 — — Compound PVD94 131 1  (0.01 mg) Example 3 — — Compound Dip 91 121 1 Example 4 — —Compound Dip 89 135 2 Example 5 — — Compound Dip 84 141 3 Example 6 — —Compound Dip 81 149 4 Example 7 — — Compound PVD 93 133 1 (0.001 mg)Example 8 — — Compound PVD 94 135 1 (0.025 mg) Comparative — — CompoundDip 77 151 example 1 5 Comparative — — — — 76 150 example 2 * “—”indicates no coating. *PVD throughput represents the weight perelectrode.

(Preparation of Electrolytic Solution)

Ethylene carbonate, monofluoroethylene carbonate as a high-permittivitysolvent and ethyl methyl carbonate as a low-viscosity solvent were mixedso as to satisfy a volume ratio 20:10:70. To the solvent mixture, LiPF₆was added so as to satisfy a concentration of 1.0 mole/liter to obtain anonaqueous electrolytic solution.

(Production of Lithium Ion Secondary Battery)

LiNi_(0.5)Mn_(1.5)O₂ was used as a positive electrode active material.Carbon black was used as a conductive material. A dispersion ofpolyvinylidene fluoride (PVdF) in N-methyl-2-pyrrolidone was used as abinding agent. The active material, conductive material and bindingagent were mixed so as to satisfy a solid content ratio of 90/4/6 (mass% ratio) to prepare a slurry-state positive-electrode mixture. Theslurry-state positive-electrode mixture obtained was uniformly appliedto an aluminum-foil current collector having a thickness of 20 μm, driedand compression-molded by a press machine to obtain a positive electrodelaminate. The positive electrode laminate was punched by a punchingmachine to obtain circular positive electrode materials having adiameter of 1.6 cm.

A lithium ion secondary battery was produced in the same manner as aboveexcept the aforementioned conditions.

(Determination of Battery Characteristics)

The cycle capacity retention rates and resistance increase rates of thecoin-type lithium ion secondary batteries obtained were checked asfollows.

(Residual Capacity Rate)

The secondary batteries produced above were charged with a currentcorresponding to 0.5 C up to 4.9 V (refers to constant current/constantvoltage charging (hereinafter referred to as “CC/CV charging”)(0.1 Ccut) at 25° C.; thereafter discharged with a constant current of 0.5 Cup to 3 V. This operation was defined as a single cycle. The initialdischarge capacity was obtained from the discharge capacity at the thirdcycle. The unit 1 C herein represents a current value when the referencecapacity of a battery is discharged in one hour. For example, 0.5 Crepresents ½ of the current value. The batteries were charged again upto 4.9 V in accordance with the CC/CV charging (0.1 C cut) andthereafter, stored at a high temperature of 85° C. for 18 hours. Afterthe storage, the batteries were discharged at 25° C. and 0.5 C up to 3V. This is specified as a residual capacity. After storage at hightemperature, the residual capacity was measured. The ratio of theresidual capacity relative to the initial discharge capacity wasobtained and specified as a residual capacity rate (%).(Residual capacity)/(Initial discharge capacity)×100=Residual capacityrate (%)

(Resistance Increase Rate)

A charge and discharge cycle performed in predetermined conditions(charged at 0.5 C under a predetermined voltage until the chargingcurrent became 0.1 C and discharged at a current corresponding to 1 C upto 3.0 V) was defined as a single cycle. The resistance after 3 cyclesand the resistance after 200 cycles were measured. The measurementtemperature was set to be 25° C. A resistance increase rate was obtainedbased on the following expression. The results are shown in Table 2.Resistance increase rate (%)=Resistance after 200 cycles (Ω)/Resistance(Ω) after 3 cycles×100

TABLE 2 Compound for coating Residual Resistance Treatment capacityincrease Positive method Negative Treatment rate rate electrode(throughput) electrode method (%) (%) Example 9 Compound 1 PVD Compound1 PVD 88 151  (0.01 mg) (0.01 mg) Example 10 Compound 1 PVD — — 87 150 (0.01 mg) Example 11 Compound 1 Dip — — 85 144 Example 12 Compound 2Dip — — 84 161 Example 13 Compound 3 Dip — — 77 181 Example 14 Compound4 Dip — — 74 183 Example 15 Compound 1 PVD — — 84 155 (0.0001 mg)Example 16 Compound 1 PVD — — 85 153 (0.0003 mg) Example 17 Compound 1PVD — — 86 152 (0.0005 mg) Example 18 Compound 1 PVD — — 87 151  (0.001mg) Example 19 Compound 1 PVD — — 86 150  (0.03 mg) Example 20 Compound1 PVD — — 85 145  (0.05 mg) Comparative Compound 5 Dip — — 71 199example 3 Comparative — — — — 70 168 example 4

As is apparent from the above results, cycle capacity characteristics orresidual capacity rate and resistance increase rate of batteries wereimproved by using the electrode of the present invention coated with aperfluoropolyether group-containing compound. Particularly, in the casesof using a perfluoropolyether group-containing silane compound and aperfluoropolyether group-containing alcohol compound, particularly inthe cases of using a perfluoropolyether group-containing silanecompound, the effects were remarkable.

INDUSTRIAL APPLICABILITY

The alkali metal battery of the present invention, since it is excellentin cycle characteristics, can be usefully used various electronics,particularly electronics having a high frequency of use, such as smartphones, mobile phones, tablet terminals and laptop computers.

What is claimed is:
 1. An electrochemical device which is an alkalimetal battery or an alkaline earth metal battery wherein only a positiveelectrode is an electrode having a perfluoropolyether group-containingcompound in a surface thereof, wherein the perfluoropolyethergroup-containing compound is a compound represented by the followingformula (A1), (A2), (C1), (C2), (D1), (D2), (E1) or (E2):

wherein: Rf each independently represents an alkyl group having 1 to 16carbon atoms optionally substituted with one or more fluorine atoms;PFPE each independently represents—(OC₆F₁₂)_(a)—(OC₅F₁₀)_(b)—(OC₄F₈)_(c)—(OC₃F₆)_(d)—(OC₂F₄)_(e)—(OCF₂)_(f)—,wherein a, b, c, d, e and f each independently represent an integer of 0or more and 200 or less, and the sum of a, b, c, d, e and f is at least1, the repeating units enclosed in parentheses attached with a, b, c, d,e or f are present in any order; R¹ each independently in eachoccurrence represents a hydrogen atom or an alkyl group having 1 to 22carbon atoms; R² each independently in each occurrence represents ahydroxyl group or a hydrolyzable group; R¹¹ each independently in eachoccurrence represents a hydrogen atom or a halogen atom; R¹² eachindependently in each occurrence represents a hydrogen atom or a loweralkyl group; n represents an integer of 0 to 3 independently for each(—SiR¹ _(n)R² _(3-n)) unit; provided that, in formulae (A1) and (A2), atleast one R² is present; X¹ each independently represents a single bondor a 2 to 10 valent organic group; X² each independently in eachoccurrence represents a single bond or a divalent organic group; t eachindependently in each occurrence represents an integer of 1 to 10; αeach independently represents an integer of 1 to 9; α′ represents aninteger of 1 to 9; X⁷ each independently represents a single bond or a 2to 10 valent organic group; γ each independently represents an integerof 1 to 9; γ′ represents an integer of 1 to 9; R^(a) each independentlyin each occurrence represents —Z—SiR⁷¹ _(p)R⁷² _(q)R⁷³ _(r); Z eachindependently in each occurrence represents an oxygen atom or a divalentorganic group; R⁷¹ each independently in each occurrence representsR^(a′); R^(a′) is the same as defined in R^(a); in R^(a), the number ofSi linearly connected via Group Z, is at most 5; R⁷² each independentlyin each occurrence represents a hydroxyl group or a hydrolyzable group;R⁷³ each independently in each occurrence represents a hydrogen atom ora lower alkyl group; p each independently in each occurrence representsan integer of 0 to 3; q each independently in each occurrence representsan integer of 0 to 3; r each independently in each occurrence representsan integer of 0 to 3; provided that, the sum of p, q and r is 3 for each—Z—SiR⁷¹ _(p)R⁷² _(q)R⁷³ _(r), and at least one R⁷² is present informulae (C1) and (C2); R^(b) each independently in each occurrencerepresents a hydroxyl group or a hydrolyzable group; R^(C) eachindependently in each occurrence represents a hydrogen atom or a loweralkyl group; k each independently in each occurrence represents aninteger of 1 to 3; l each independently in each occurrence represents aninteger of 0 to 2; m each independently in each occurrence represents aninteger of 0 to 2; provided that, in the unit enclosed in parenthesesattached with γ, the sum of k, l and m is 3; X⁹ each independentlyrepresents a single bond or a 2 to 10 valent organic group; δ eachindependently represents an integer of 1 to 9; δ′ represents an integerof 1 to 9; R^(d) each independently in each occurrence represents—Z′—CR⁸¹ _(p′)R⁸² _(q′)R⁸³ _(r′); Z′ each independently in eachoccurrence represents an oxygen atom or a divalent organic group; R⁸¹each independently in each occurrence represents R^(d′); R^(d′) is thesame as defined in R^(d); in R^(d), the number of C linearly connectedvia group Z′ is at most 5; R⁸² each independently in each occurrencerepresents —Y—SiR⁸⁵ _(j)R⁸⁶ _(3-j); Y each independently in eachoccurrence represents a divalent organic group; R⁸⁵ each independentlyin each occurrence represents a hydroxyl group or a hydrolyzable group;R⁸⁶ each independently in each occurrence represents a hydrogen atom ora lower alkyl group; j represents an integer of 1 to 3 independently foreach (—Y—SiR⁸⁵ _(j)R⁸⁶ _(3-j)) unit; R⁸³ each independently in eachoccurrence represents a hydrogen atom or a lower alkyl group; p′ eachindependently in each occurrence represents an integer of 0 to 3; q′each independently in each occurrence represents an integer of 0 to 3;r′ each independently in each occurrence represents an integer of 0 to3; R^(e) each independently in each occurrence represents —Y—SiR⁸⁵_(j)R⁸⁶ _(3-j); R^(f) each independently in each occurrence represents ahydrogen atom or a lower alkyl group; k′ each independently in eachoccurrence represents an integer of 0 to 3; l′ each independently ineach occurrence represents an integer of 0 to 3; m′ each independentlyin each occurrence represents an integer of 0 to 3; provided that, inthe formula, at least one q′ represents an integer of 2 or 3 or at leastone l′ represents an integer of 2 or 3; X³ each independently representsa single bond or a 2 to 10 valent organic group; ε each represents aninteger of 1 to 9; ε′ each independently represents an integer of 1 to9; and A each independently in each occurrence represents —OH, —SH,—NH₂, —COOH or —SO₃H.
 2. The electrochemical device according to claim1, wherein the perfluoropolyether group-containing compound is presentas a coating layer.
 3. The electrochemical device according to claim 1,wherein the perfluoropolyether group-containing compound is a compoundrepresented by formula (A1), (A2), (C1), (C2), (D1) or (D2).